Advanced animations - Web APIs
var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var ball = { x: 100, y: 100, radius: 25, color: 'blue', draw: function() { ctx.beginpath(); ctx.arc(this.x, this.y, this.radius, 0, math.pi * 2, true); ctx.closepath(); ctx.fillstyle = this.color; ctx.fill(); } }; ball.draw(); nothing special here, the ball is actually a simple circle and gets drawn with the help of ...
... var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var raf; var ball = { x: 100, y: 100, vx: 5, vy: 2, radius: 25, color: 'blue', draw: function() { ctx.beginpath(); ctx.arc(this.x, this.y, this.radius, 0, math.pi * 2, true); ctx.closepath(); ctx.fillstyle = this.color; ctx.fill(); } }; function draw() { ctx.clearrect(0,0, canvas.width, canvas.height); ball.dr...
... <canvas id="canvas" style="border: 1px solid" width="600" height="300"></canvas> var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var raf; var ball = { x: 100, y: 100, vx: 5, vy: 2, radius: 25, color: 'blue', draw: function() { ctx.beginpath(); ctx.arc(this.x, this.y, this.radius, 0, math.pi * 2, true); ctx.closepath(); ctx.fillstyle = this.color; ctx.fill(); } }; function draw() { ctx.clearrect(0,0, canvas.width, canvas.height); ball.dr...
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EventTarget.addEventListener() - Web APIs
html <table id="outside"> <tr><td id="t1">one</td></tr> <tr><td id="t2">two</td></tr> </table> javascript // function to change the content of t2 function modifytext() { const t2 = document.getelementbyid("t2"); if (t2.firstchild.nodevalue == "three") { t2.firstchild.nodevalue = "two"; } else { t2.firstchild.nodevalue = "three"; } } // add event listener to table const el = document.getelementbyid("outside"); el.addeventlistener("click", modifytext, false); in this code, modifytext() is a listener for click events registered using addeventlistener().
... html <table id="outside"> <tr><td id="t1">one</td></tr> <tr><td id="t2">two</td></tr> </table> javascript // function to change the content of t2 function modifytext(new_text) { const t2 = document.getelementbyid("t2"); t2.firstchild.nodevalue = new_text; } // function to add event listener to table const el = document.getelementbyid("outside"); el.addeventlistener("click", function(){modifytext("four")}, false); notice that the listener is an anonymous function that encapsulates code that is then, in turn, able to send parameters to the modifytext() function, which is responsible for actually respon...
... html <table id="outside"> <tr><td id="t1">one</td></tr> <tr><td id="t2">two</td></tr> </table> javascript // function to change the content of t2 function modifytext(new_text) { const t2 = document.getelementbyid("t2"); t2.firstchild.nodevalue = new_text; } // add event listener to table with an arrow function const el = document.getelementbyid("outside"); el.addeventlistener("click", () => { modifytext("four"); }, false); result please note that while anonymous and arrow functions are similar, they have different this bindings.
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Signaling and video calling - Web APIs
that would be weird."); return; } targetusername = clickedusername; createpeerconnection(); navigator.mediadevices.getusermedia(mediaconstraints) .then(function(localstream) { document.getelementbyid("local_video").srcobject = localstream; localstream.gettracks().foreach(track => mypeerconnection.addtrack(track, localstream)); }) .catch(handlegetusermediaerror); } } this begins with a basic sanity check: is the user already connected?
... function handlevideooffermsg(msg) { var localstream = null; targetusername = msg.name; createpeerconnection(); var desc = new rtcsessiondescription(msg.sdp); mypeerconnection.setremotedescription(desc).then(function () { return navigator.mediadevices.getusermedia(mediaconstraints); }) .then(function(stream) { localstream = stream; document.getelementbyid("local_video").srcobject = localstream; localstream.gettracks().foreach(track => mypeerconnection.addtrack(track, localstream)); }) .then(function() { return mypeerconnection.createanswer(); }) .then(function(answer) { return mypeerconnection.setlocaldescription(answer); }) .then(function() { var msg = { name: myusername, target: targetusername, type...
...in our example, we add the track's stream to the <video> element that displays the incoming video: function handletrackevent(event) { document.getelementbyid("received_video").srcobject = event.streams[0]; document.getelementbyid("hangup-button").disabled = false; } the incoming stream is attached to the "received_video" <video> element, and the "hang up" <button> element is enabled so the user can hang up the call.
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Cubic Bezier Generator - CSS: Cascading Style Sheets
ge="updatecanvas();return true;" type="text" maxlength=6 id="x2" value="0.14" class='field'> <label for="y2">y2 = </label><input onchange="updatecanvas();return true;" type="text" maxlength=6 id="y2" value="0.53" class='field'> <br> <output id="output">log</output> </form> </html> .field { width: 40px; } function updatecanvas() { var x1 = document.getelementbyid('x1').value; var y1 = document.getelementbyid('y1').value; var x2 = document.getelementbyid('x2').value; var y2 = document.getelementbyid('y2').value; drawbeziercurve(x1, y1, x2, y2); } const radius = 4; // place needed to draw the rulers const rulers = 30.5; const margin = 10.5; const basic_scale_size = 5; // size of 0.1 tick on the rulers var scaling; //limitation: scaling is ...
...computed once: if canvas.height/canvas.width change it won't be recalculated var dragsm = 0; // drag state machine: 0 = nodrag, others = object being dragged function initcanvas() { // get the canvas element using the dom var canvas = document.getelementbyid('bezier'); // make sure we don't execute when canvas isn't supported if (canvas.getcontext) { // use getcontext to use the canvas for drawing var ctx = canvas.getcontext('2d'); scaling = math.min(canvas.height - rulers - margin, canvas.width - rulers - margin); canvas.onmousedown = mousedown; canvas.onmouseup = mouseup; } else { alert('you need safari or firefox 1.5+ to see this demo.'); } } function cx(x) { return x * scaling + rulers; } function reversex(x) { ret...
...result + 0.5 : result; } function drawbeziercurve(x1, y1, x2, y2) { // get the canvas element using the dom var canvas = document.getelementbyid('bezier'); // make sure we don't execute when canvas isn't supported if (canvas.getcontext) { // use getcontext to use the canvas for drawing var ctx = canvas.getcontext('2d'); // clear canvas ctx.clearrect(0, 0, canvas.width, canvas.height); // draw the rulers ctx.beginpath(); ctx.strokestyle = "black"; // draw the y ...
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ui/frame - Archive of obsolete content
// city-info.js var cityselector = window.document.getelementbyid("city-selector"); cityselector.addeventlistener("change", citychanged); function citychanged() { window.parent.postmessage(cityselector.value, "*"); } to listen for these messages in the main add-on code, you can assign a listener to the frame's message event.
...; var toolbar = toolbar({ name: "city-info", title: "city info", items: [frame] }); function updateweather(location) { frame.postmessage(weather[location], frame.url); } to listen to these messages in the frame script, add a listener to the window's message event: window.addeventlistener("message", updateweather, false); function updateweather(message) { var label = window.document.getelementbyid("weather"); label.textcontent = message.data; } from add-on to a specific frame you can send a message from the main add-on code to the frame hosted by a particular browser window.
...if you send a json object, the sdk takes care of serializing and deserializing it for you: // frame.js var label = window.document.getelementbyid("linky"); label.addeventlistener("click", function() { window.parent.postmessage({ "type" : "ping", "reason" : "they clicked me" }, "*"); }, true); // main.js var { frame } = require("sdk/ui/frame"); var frame = new frame({ url: "./frame.html" }); frame.on("message", pong); function pong(e) { if (e.data.type == "ping") { console.log(e.data.reason); e.source.postmess...
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XUL Questions and Answers - Archive of obsolete content
an example of this is: var tree = document.getelementbyid('treeid'); selectedtreeitem = tree.view.getitematindex(tree.currentindex); selectedtreeitem.firstchild.setattribute('style', 'background: #ff0000'); what is an example of tab browser in xul?
... using the following code sample, // get browsers object var browsers=document.getelementbyid('content').browsers; var numbrowsers=browsers.length; for (var i=0; numbrowsers>i; i++) { var thisuri=browsers[i].currenturi.spec; // do something with it.
... if you have a similar code base as the following: onbookmarkcontextmenu: function(event, id) { document.getelementbyid("bookmarkpopup").showpopup(document.getelementbyid(id), event.screenx + 6, event.screeny + 6, "popup", "bottomright", "bottomright"); } use the hidepopup() function to solve this issue.
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Using the W3C DOM - Archive of obsolete content
accessing elements with the w3c dom the basic method for referencing elements in an html page is document.getelementbyid().
...for example, the following short sample dynamically sets the left margin of a <div> element with an id of "inset" to half an inch: // in the html: <div id="inset">sample text</div> document.getelementbyid("inset").style.marginleft = ".5in"; note: internet explorer 5 through 7 have a flawed implementation of getelementbyid(), which returns the first element with a matching name or id (id versus name when using getelementbyid, msdn: getelementbyid method).
... ie-specific ways to access elements w3c web standards replacements id_attribute_value document.getelementbyid() document.all.id_attribute_value document.getelementbyid() document.all[id_attribute_value] document.getelementbyid() formname.inputname.value document.forms["formname"].inputname.value or document.forms["formname"].elements["inputname"].value inputname.value document.forms["formname"].inputname.value or document.forms["formname"].elements["inputname"].value formctrlname document.forms["formname"].formctrlname or document.forms["formname"].elements["formctrlname"] document.forms(0) document.forms[0] more on accessing forms and form elements: referencing forms and form controls b...
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Browser Detection and Cross Browser Support - Archive of obsolete content
if (document.all) { // ie4 height = document.body.offsetheight; } else if (document.layers) { // nn4 height = window.innerheight; } else { // other height = 0; } with the introduction of the w3c dom, the standard method document.getelementbyid became available in internet explorer 5 and later in netscape 6 (gecko).
...if (document.all) { // ie4 height = document.body.offsetheight; } else if (document.layers) { // nn4 height = window.innerheight; } else if (document.getelementbyid) { // they think this is gecko // but could be wrong!
... height = window.innerheight; } else { // other height = 0; } the approach is incorrect since it assumes that the only other browser besides internet explorer 5+ that implements document.getelementbyid is gecko.
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HTML text fundamentals - Learn web development
rried to a fish.</textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...
...ggs bread hummus</textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...
...ters up the road</textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...
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Transformations - Web APIs
function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); ctx.fillrect(0, 0, 150, 150); // draw a rectangle with default settings ctx.save(); // save the default state ctx.fillstyle = '#09f'; // make changes to the settings ctx.fillrect(15, 15, 120, 120); // draw a rectangle with new settings ctx.save(); // save the current state ctx.fillstyle = '#fff'; // make chan...
... function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); for (var i = 0; i < 3; i++) { for (var j = 0; j < 3; j++) { ctx.save(); ctx.fillstyle = 'rgb(' + (51 * i) + ', ' + (255 - 51 * i) + ', 255)'; ctx.translate(10 + j * 50, 10 + i * 50); ctx.fillrect(0, 0, 25, 25); ctx.restore(); } } } <canvas id="canvas" width="150" height="150"></canvas> draw(); screenshotlive sample rotat...
... function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); // left rectangles, rotate from canvas origin ctx.save(); // blue rect ctx.fillstyle = '#0095dd'; ctx.fillrect(30, 30, 100, 100); ctx.rotate((math.pi / 180) * 25); // grey rect ctx.fillstyle = '#4d4e53'; ctx.fillrect(30, 30, 100, 100); ctx.restore(); // right rectangles, rotate from rectangle center // draw blue rect ctx.fillstyle = '#0095dd...
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Capabilities, constraints, and settings - Web APIs
determining if a constraint is supported if you need to know whether or not a given constriant is supported by the user agent, you can find out by calling navigator.mediadevices.getsupportedconstraints() to get a list of the constrainable properties which the browser knows, like this: let supported = navigator.mediadevices.getsupportedconstraints(); document.getelementbyid("framerateslider").disabled = !supported["framerate"]; in this example, the supported constraints are fetched, and a control that lets the user configure the frame rate is disabled if the framerate constraint isn't supported.
... let videoelement = document.getelementbyid("video"); let logelement = document.getelementbyid("log"); let supportedconstraintlist = document.getelementbyid("supportedconstraints"); let videoconstrainteditor = document.getelementbyid("videoconstrainteditor"); let audioconstrainteditor = document.getelementbyid("audioconstrainteditor"); let videosettingstext = document.getelementbyid("videosettingstext"); let audiosettingstext = document.ge...
... we also need to set up an event listener to watch for the "start video" button to be clicked: document.getelementbyid("startbutton").addeventlistener("click", function() { startvideo(); }, false); applying constraint set updates next, we set up an event listener for the "apply constraints" button.
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Touch events - Web APIs
function startup() { var el = document.getelementbyid("canvas"); el.addeventlistener("touchstart", handlestart, false); el.addeventlistener("touchend", handleend, false); el.addeventlistener("touchcancel", handlecancel, false); el.addeventlistener("touchmove", handlemove, false); } document.addeventlistener("domcontentloaded", startup); this simply sets up all the event listeners for our <canvas> element so we can handle the touch events a...
... function handlestart(evt) { evt.preventdefault(); console.log("touchstart."); var el = document.getelementbyid("canvas"); var ctx = el.getcontext("2d"); var touches = evt.changedtouches; for (var i = 0; i < touches.length; i++) { console.log("touchstart:" + i + "..."); ongoingtouches.push(copytouch(touches[i])); var color = colorfortouch(touches[i]); ctx.beginpath(); ctx.arc(touches[i].pagex, touches[i].pagey, 4, 0, 2 * math.pi, false); // a circle at the start ctx.fillstyle = color; ctx.fill(); console.log("touchstart...
... function handlemove(evt) { evt.preventdefault(); var el = document.getelementbyid("canvas"); var ctx = el.getcontext("2d"); var touches = evt.changedtouches; for (var i = 0; i < touches.length; i++) { var color = colorfortouch(touches[i]); var idx = ongoingtouchindexbyid(touches[i].identifier); if (idx >= 0) { console.log("continuing touch "+idx); ctx.beginpath(); console.log("ctx.moveto(" + ongoingtouches[idx].pagex + ", " + ongoingtouche...
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Using the Web Animations API - Web APIs
bring the pieces together now it’s time to bring them both together with the element.animate() method: document.getelementbyid("alice").animate( alicetumbling, alicetiming ) and boom: the animation starts playing (see the finished version on codepen).
...instead of making objects for keyframes and timing properties, we could just pass their values in directly, like so: document.getelementbyid("alice").animate( [ { transform: 'rotate(0) translate3d(-50%, -50%, 0)', color: '#000' }, { color: '#431236', offset: 0.3}, { transform: 'rotate(360deg) translate3d(-50%, -50%, 0)', color: '#000' } ], { duration: 3000, iterations: infinity } ); what’s more, if we only wanted to specify the duration of the animation and not its iterations (by default, animations iterate once), we could pass in the milliseconds alone: document.getelementbyid("alice").animate( [ { transform: 'rotate(0) translate3d(-50%, -5...
... pausing and playing animations we’ll talk more about alice’s animation later, but for now, let’s look closer at the cupcake’s animation: var nommingcake = document.getelementbyid('eat-me_sprite').animate( [ { transform: 'translatey(0)' }, { transform: 'translatey(-80%)' } ], { fill: 'forwards', easing: 'steps(4, end)', duration: alicechange.effect.timing.duration / 2 }); the element.animate() method will immediately run after it is called.
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Audio and video manipulation - Developer guides
var processor = { timercallback: function() { if (this.video.paused || this.video.ended) { return; } this.computeframe(); var self = this; settimeout(function () { self.timercallback(); }, 16); // roughly 60 frames per second }, doload: function() { this.video = document.getelementbyid("my-video"); this.c1 = document.getelementbyid("my-canvas"); this.ctx1 = this.c1.getcontext("2d"); var self = this; this.video.addeventlistener("play", function() { self.width = self.video.width; self.height = self.video.height; self.timercallback(); }, false); }, computeframe: function() { this.ctx1.drawimage(this.video, 0, 0, this.width, this.heig...
... html <video id="my-video" controls src="https://udn.realityripple.com/samples/6f/08625b424a.m4v"> </video> javascript var myvideo = document.getelementbyid('my-video'); myvideo.playbackrate = 2; playable code <video id="my-video" controls="true" width="480" height="270"> <source src="https://udn.realityripple.com/samples/5b/8cd6da9c65.webm" type="video/webm"> <source src="https://udn.realityripple.com/samples/6f/08625b424a.m4v" type="video/mp4"> </video> <div class="playable-buttons"> <input id="edit" type="button" value="edit" /> <input ...
...id="reset" type="button" value="reset" /> </div> <textarea id="code" class="playable-code"> var myvideo = document.getelementbyid('my-video'); myvideo.playbackrate = 2;</textarea> var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var edit = document.getelementbyid('edit'); var code = textarea.value; function setplaybackrate() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; setplaybackrate(); }); edit.addeventlistener('click', function() { textarea.focus(); }) textarea.addeventlistener('input', setplaybackrate); window.addeventlistener('load', setplaybackrate); note: try the playbackrate example live.
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HTML to DOM - Archive of obsolete content
p><p>bar</p>'); alert(dompars.getelementsbytagname('p').length); if htmlparser() returns the element name html (instead of body), you have all document object with its complete functions list, therefore you can retrieve info within div tag like this: var dompars = htmlparser("<div id='userinfo'>john was a mediocre programmer, but people liked him <strong>anyway</strong>.</div>"); alert(dompars.getelementbyid('userinfo').innerhtml); to parse a complete html page, load it into an iframe whose type is content (not chrome).
... var frame = document.getelementbyid("sample-frame"); if (!frame) { // create frame frame = document.createelement("iframe"); // iframe (or browser on older firefox) frame.setattribute("id", "sample-frame"); frame.setattribute("name", "sample-frame"); frame.setattribute("type", "content"); frame.setattribute("collapsed", "true"); document.getelementbyid("main-window").appendchild(frame); // or // document.documente...
...unction (event) { // the document of the html in the dom var doc = event.originaltarget; // skip blank page or frame if (doc.location.href == "about:blank" || doc.defaultview.frameelement) return; // do something with the dom of doc alert(doc.location.href); // when done remove frame or set location "about:blank" settimeout(function (){ var frame = document.getelementbyid("sample-frame"); // remove frame // frame.destroy(); // if using browser element instead of iframe frame.parentnode.removechild(frame); // or set location "about:blank" // frame.contentdocument.location.href = "about:blank"; },10); }, true); } // load a page frame.contentdocument.location.href = "http://www.mozilla.org/"; // or // frame.webnavigation.lo...
... <vbox hidden="false" height="0"> <iframe type="content" src="" name="donkey-browser" hidden="false" id="donkey-browser" height="0"/> </vbox> then, in your extension's "load" event handler: onload: function() { donkeybrowser = document.getelementbyid("donkey-browser"); if (donkeybrowser) { donkeybrowser.style.height = "0px"; donkeybrowser.webnavigation.allowauth = true; donkeybrowser.webnavigation.allowimages = false; donkeybrowser.webnavigation.allowjavascript = false; donkeybrowser.webnavigation.allowmetaredirects = true; donkeybrowser.webnavigation.allowplugins = false; donkeybrowser.webnavigation.allowsubframes = false; d...

Appendix C: Avoiding using eval in Add-ons - Archive of obsolete content
// do not use eval(document.getelementbyid("mymenu").getattribute("oncommand")); eval(document.getelementbyid("mylabel").getattribute("onclick")); alternative: dispatch real events dispatching real events has the added bonus that all other event listeners for that element (and the corresponding bubbling/capturing chain) will fire as well, so this method will have the closed resemblance to a real user event.
... // fake a command event var event = document.createevent("events"); event.initevent("command", true, true); document.getelementbyid("mymenu").dispatchevent(event); // fake a mouse click var mouseevent = document.createevent("mouseevents"); event.initmouseevent("click", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null); document.getelementbyid("mylabel").dispatchevent(mouseevent); please see the corresponding documentation on how to use and initialize particular event types.
... document.getelementbyid("mybutton").click(); alternative: element.docommand() xul elements that have a command (oncommand or command attribute) assigned will also have a working docommand method.
... document.getelementbyid("mymenu").docommand(); alternative: just hard-code what should happen if you know that the current version of the application will call { executesomething(); executesomethingelse();} then just do the same in your code.

Inner-browsing extending the browser navigation paradigm - Archive of obsolete content
note the following piece of code: function iframecallback(doc) { /* copies the data in the iframe to the main page */ mydata = doc.getelementbyid("mydata"); tickerdiv.innerhtml = mydata.innerhtml; } the callback is called with the parameter doc, which is a reference to the iframe's document).
... document.getelementbyid("container").innerhtml+=articletitle+"<br />"; } source code for the sample <html> <head> <title>inner-browsing example, with xmlhttprequest and dom</title> <script type="text/javascript" language="javascript" src="xmlrequest.js"></script> <script> /* ***** begin license block ***** * version: mpl 1.1 * * the contents of this file are subject to the mozilla public license version * 1.1 (the...
... * * contributor(s): marcio galli <mgalli@mgalli.com> * * ***** end license block ***** */ //// /// calldevedge represents the inner-browsing function here // function calldevedge(loaddata,ele) { var x = new xmlremoterequest(); doc=x.getremotedocument(loaddata); document.getelementbyid("container").innerhtml=""; if(doc!=null) { tagname="article"; // ie fix if(document.all) tagname="nde:"+tagname; articles=doc.getelementsbytagname(tagname); for(i=0;i<articles.length;i++) { article=articles.item(i); tagname="title"; // ie fix if(document.all) tagname="nde:"+tagname; valuee=article.getelementsbytagname...
...em(0).firstchild.nodevalue; tagname="summary"; // ie fix if(document.all) tagname="nde:"+tagname; paraa=article.getelementsbytagname(tagname).item(0).firstchild.nodevalue; linkk=article.getattribute("url"); strvalue="<div class='nde-blurb'><h3><a href='"+linkk+"'>"+valuee+"</a></h3><p>"+paraa+"</p></div>"; document.getelementbyid("container").innerhtml+=strvalue; } } if(previousele) { previousele.style.backgroundcolor="white"; } ele.style.backgroundcolor="#ddeeff"; previousele=ele; } var previousele=null; </script> <style> .tab { position:relative;top:1px; border: 1px solid #dddddd; color:white; background-color:white; padding-left: 5px; border-bottom:white;padding-right: 5px; padding-top:3px; text-dec...

Manipulating Lists - Archive of obsolete content
here is an example: example 1 : source view <script> function additem(){ document.getelementbyid('thelist').appenditem("thursday", "thu"); } </script> <listbox id="thelist"/> <button label="add" oncommand="additem();"/> the appenditem() takes two arguments, the label, in this case 'thursday', and a value 'thu'.
... example 3 : source view <script> function doselect(){ var val = document.getelementbyid('number').value; val = number(val); if (val != null) document.getelementbyid('level').selectedindex = val - 1; } </script> <hbox align="center"> <label value="enter a number from 1 to 3:"/> <textbox id="number"/> <button label="select" oncommand="doselect();"/> </hbox> <radiogroup id="level"> <radio label="excellent"/> <radio label="good"/> <radio label="poor"/> </radiogroup...
... deleting selected items the following example shows a method of deleting the selected items properly: example 4 : source view <script> function deleteselection(){ var list = document.getelementbyid('thelist'); var count = list.selectedcount; while (count--){ var item = list.selecteditems[0]; list.removeitemat(list.getindexofitem(item)); } } </script> <button label="delete" oncommand="deleteselection();"/> <listbox id="thelist" seltype="multiple"> <listitem label="cheddar"/> <listitem label="cheshire"/> <listitem label="edam"/> <listitem label="gouda"/> <listitem la...
...compare the effect of both functions at different scroll positions in this example: example 5 : source view <button label="scrolltoindex" oncommand="document.getelementbyid('thelist').scrolltoindex(4);"/> <button label="ensureindexisvisible" oncommand="document.getelementbyid('thelist').ensureindexisvisible(4);"/> <listbox id="thelist" rows="5"> <listitem label="1"/> <listitem label="2"/> <listitem label="3"/> <listitem label="4"/> <listitem label="5"/> <listitem label="6"/> <listitem label="7"/> <listitem label="8"/> <listitem label="9...

Browser Feature Detection - Archive of obsolete content
ateentityreference()obsolete since gecko 7 true false false document.getelementsbytagname() true true true document.importnode() true false true document.createelementns() true false true document.createattributens() true false true document.getelementsbytagnamens() true false true document.getelementbyid() true true true dom level 1 html support for properties/methods in document name firefox 1.5 ie 6 & 7 opera 8.54 - 9.01 document.documentelement true true true document.createelement() true true true document.createdocumentfragment() true true true document.createtextnode() true true tru...
...ent.links true true true document.forms true true true document.anchors true true true document.cookie true true true document.open() true true true document.close() true true true document.write() true true true document.writeln() true true true document.getelementbyid() true true true document.getelementsbyname() true true true dom css 1 support for properties/methods in document.body.style name firefox 1.5 ie 6 & 7 opera 8.54 - 9.01 background true true true backgroundattachment true true true backgroundcolor true true true backgroundimage t...
...: 'images', 'supported': false}, {name: 'applets', 'supported': false}, {name: 'links', 'supported': false}, {name: 'forms', 'supported': false}, {name: 'anchors', 'supported': false}, {name: 'cookie', 'supported': false}, {name: 'open', 'supported': false}, {name: 'close', 'supported': false}, {name: 'write', 'supported': false}, {name: 'writeln', 'supported': false}, {name: 'getelementbyid', 'supported': false}, {name: 'getelementsbyname', 'supported': false} ], 'domcore2': [ {name: 'doctype', 'supported': false}, {name: 'implementation', 'supported': false}, {name: 'documentelement', 'supported': false}, {name: 'createelement', 'supported': false}, {name: 'createdocumentfragment', 'supported': false}, {name: 'createtextnode', 'supported': false}, {name: 'createc...
...ruction', 'supported': false}, {name: 'createattribute', 'supported': false}, {name: 'createentityreference', 'supported': false}, {name: 'getelementsbytagname', 'supported': false}, {name: 'importnode', 'supported': false}, {name: 'createelementns', 'supported': false}, {name: 'createattributens', 'supported': false}, {name: 'getelementsbytagnamens', 'supported': false}, {name: 'getelementbyid', 'supported': false} ], 'domcss1': [ {name: 'background', 'supported': false}, {name: 'backgroundattachment', 'supported': false}, {name: 'backgroundcolor', 'supported': false}, {name: 'backgroundimage', 'supported': false}, {name: 'backgroundrepeat', 'supported': false}, {name: 'border', 'supported': false}, {name: 'borderspacing', 'supported': false}, {name: 'borderstyle', '...

CanvasRenderingContext2D.arcTo() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // tangential lines ctx.beginpath(); ctx.strokestyle = 'gray'; ctx.moveto(200, 20); ctx.lineto(200, 130); ctx.lineto(50, 20); ctx.stroke(); // arc ctx.beginpath(); ctx.strokestyle = 'black'; ctx.linewidth = 5; ctx.moveto(200, 20); ctx.arcto(200,130, 50,20, 40); ctx.stroke(); // start point ctx.beginpath(); ctx.fillstyle = 'blue'; ctx.arc(200, 20,...
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const p0 = { x: 230, y: 20 } const p1 = { x: 90, y: 130 } const p2 = { x: 20, y: 20 } const labelpoint = function (p) { const offset = 15; ctx.filltext('(' + p.x + ',' + p.y + ')', p.x + offset, p.y + offset); } ctx.beginpath(); ctx.moveto(p0.x, p0.y); ctx.arcto(p1.x, p1.y, p2.x, p2.y, 50); ctx.lineto(p2.x, p2.y); labelpoint(p0); labelpo...
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(180, 90); ctx.arcto(180,130, 110,130, 130); ctx.lineto(110, 130); ctx.stroke(); result live demo more sophisticated demo of the method.
... html <div> <label for="radius">radius: </label> <input name="radius" type="range" id="radius" min=0 max=100 value=50> <label for="radius" id="radius-output">50</label> </div> <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const controlout = document.getelementbyid('radius-output'); const control = document.getelementbyid('radius'); control.oninput = () => { controlout.textcontent = r = control.value; }; const mouse = { x: 0, y: 0 }; let r = 100; // radius const p0 = { x: 0, y: 50 }; const p1 = { x: 100, y: 100 }; const p2 = { x: 150, y: 50 }; const p3 = { x: 200, y: 100 }; const labelpoint = function (p, offset, i ...

Basic usage of canvas - Web APIs
var canvas = document.getelementbyid('tutorial'); var ctx = canvas.getcontext('2d'); the first line in the script retrieves the node in the dom representing the <canvas> element by calling the document.getelementbyid() method.
...our code snippet from above becomes something like this: var canvas = document.getelementbyid('tutorial'); if (canvas.getcontext) { var ctx = canvas.getcontext('2d'); // drawing code here } else { // canvas-unsupported code here } a skeleton template here is a minimalistic template, which we'll be using as a starting point for later examples.
... <!doctype html> <html> <head> <meta charset="utf-8"/> <title>canvas tutorial</title> <script type="text/javascript"> function draw() { var canvas = document.getelementbyid('tutorial'); if (canvas.getcontext) { var ctx = canvas.getcontext('2d'); } } </script> <style type="text/css"> canvas { border: 1px solid black; } </style> </head> <body onload="draw();"> <canvas id="tutorial" width="150" height="150"></canvas> </body> </html> the script includes a function called draw(), which is executed once the page finishes loading; this is done by listening for the load event on the document.
... <!doctype html> <html> <head> <meta charset="utf-8"/> <script type="application/javascript"> function draw() { var canvas = document.getelementbyid('canvas'); if (canvas.getcontext) { var ctx = canvas.getcontext('2d'); ctx.fillstyle = 'rgb(200, 0, 0)'; ctx.fillrect(10, 10, 50, 50); ctx.fillstyle = 'rgba(0, 0, 200, 0.5)'; ctx.fillrect(30, 30, 50, 50); } } </script> </head> <body onload="draw();"> <canvas id="canvas" width="150" height="150"></canvas> </body> </html> this exam...

Drawing text - Web APIs
function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); ctx.font = '48px serif'; ctx.filltext('hello world', 10, 50); } <canvas id="canvas" width="300" height="100"></canvas> draw(); a stroketext example the text is filled using the current strokestyle.
... function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); ctx.font = '48px serif'; ctx.stroketext('hello world', 10, 50); } <canvas id="canvas" width="300" height="100"></canvas> draw(); styling text in the examples above we are already making use of the font property to make the text a bit larger than the default size.
...able code <canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas> <div class="playable-buttons"> <input id="edit" type="button" value="edit" /> <input id="reset" type="button" value="reset" /> </div> <textarea id="code" class="playable-code"> ctx.font = "48px serif"; ctx.textbaseline = "hanging"; ctx.stroketext("hello world", 0, 100);</textarea> var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var edit = document.getelementbyid('edit'); var code = textarea.value; function drawcanvas() { ctx.clearrect(0, 0, canvas.width, canvas.height); eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; drawcanvas()...
... function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); var text = ctx.measuretext('foo'); // textmetrics object text.width; // 16; } gecko-specific notes in gecko (the rendering engine of firefox, firefox os and other mozilla based applications), some prefixed apis were implemented in earlier versions to draw text on a canvas.

Pixel manipulation with canvas - Web APIs
<canvas id="canvas" width="300" height="227" style="float:left"></canvas> <div id="color" style="width:200px;height:50px;float:left"></div> var img = new image(); img.src = 'https://mdn.mozillademos.org/files/5397/rhino.jpg'; var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); img.onload = function() { ctx.drawimage(img, 0, 0); img.style.display = 'none'; }; var color = document.getelementbyid('color'); function pick(event) { var x = event.layerx; var y = event.layery; var pixel = ctx.getimagedata(x, y, 1, 1); var data = pixel.data; var rgba = 'rgba(' + data[0] + ', ' + data[1] + ', ' + data[2] + ...
... <canvas id="canvas" width="300" height="227"></canvas> <div> <input id="grayscalebtn" value="grayscale" type="button"> <input id="invertbtn" value="invert" type="button"> </div> var img = new image(); img.src = 'https://mdn.mozillademos.org/files/5397/rhino.jpg'; img.onload = function() { draw(this); }; function draw(img) { var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.drawimage(img, 0, 0); img.style.display = 'none'; var imagedata = ctx.getimagedata(0, 0, canvas.width, canvas.height); var data = imagedata.data; var invert = function() { for (var i = 0; i < data.length; i += 4) { data[i] = 255 - data[i]; // red data[i + 1] = 255 - data[i + 1]; // green data[i + 2] = 255...
... - data[i + 2]; // blue } ctx.putimagedata(imagedata, 0, 0); }; var grayscale = function() { for (var i = 0; i < data.length; i += 4) { var avg = (data[i] + data[i + 1] + data[i + 2]) / 3; data[i] = avg; // red data[i + 1] = avg; // green data[i + 2] = avg; // blue } ctx.putimagedata(imagedata, 0, 0); }; var invertbtn = document.getelementbyid('invertbtn'); invertbtn.addeventlistener('click', invert); var grayscalebtn = document.getelementbyid('grayscalebtn'); grayscalebtn.addeventlistener('click', grayscale); } zooming and anti-aliasing with the help of the drawimage() method, a second canvas and the imagesmoothingenabled property, we are able to zoom into our picture and see the details.
...eight="227"></canvas> <canvas id="zoom" width="300" height="227"></canvas> <div> <label for="smoothbtn"> <input type="checkbox" name="smoothbtn" checked="checked" id="smoothbtn"> enable image smoothing </label> </div> var img = new image(); img.src = 'https://mdn.mozillademos.org/files/5397/rhino.jpg'; img.onload = function() { draw(this); }; function draw(img) { var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.drawimage(img, 0, 0); img.style.display = 'none'; var zoomctx = document.getelementbyid('zoom').getcontext('2d'); var smoothbtn = document.getelementbyid('smoothbtn'); var togglesmoothing = function(event) { zoomctx.imagesmoothingenabled = this.checked; zoomctx.mozimagesmoothingenabled = this.checked; zoomctx.webkitimagesm...

Pointer events - Web APIs
nt) { } function enter_handler(event) { } function down_handler(event) { } function move_handler(event) { } function up_handler(event) { } function cancel_handler(event) { } function out_handler(event) { } function leave_handler(event) { } function gotcapture_handler(event) { } function lostcapture_handler(event) { } function init() { var el=document.getelementbyid("target"); // register pointer event handlers el.onpointerover = over_handler; el.onpointerenter = enter_handler; el.onpointerdown = down_handler; el.onpointermove = move_handler; el.onpointerup = up_handler; el.onpointercancel = cancel_handler; el.onpointerout = out_handler; el.onpointerleave = leave_handler; el.gotpointercapture = gotc...
... + ev.pointertype + " is not suported"); } // call the tilt handler if (ev.tiltx != 0 && ev.tilty != 0) process_tilt(ev.tiltx, ev.tilty); // call the pressure handler process_pressure(ev.pressure); // if this event is not primary, call the non primary handler if (!ev.isprimary) process_non_primary(ev); } function init() { var el=document.getelementbyid("target"); // register pointerdown handler el.onpointerdown = down_handler; } </script> <body onload="init();"> <div id="target"> touch me ...
... <html> <script> function downhandler(ev) { let el = document.getelementbyid("target"); // element 'target' will receive/capture further events el.setpointercapture(ev.pointerid); } function init() { let el = document.getelementbyid("target"); el.onpointerdown = downhandler; } </script> <body onload="init();"> <div id="target"> touch me ...
... <html> <script> function downhandler(ev) { let el = document.getelementbyid("target"); // element "target" will receive/capture further events el.setpointercapture(ev.pointerid); } function cancelhandler(ev) { let el = document.getelementbyid("target"); // release the pointer capture el.releasepointercapture(ev.pointerid); } function init() { let el = document.getelementbyid("target"); // register pointerdown and pointercancel handlers el.onpointerdown = downhandler; el.onpointercancel = cancelhandler; } </scri...

Writing WebSocket client applications - Web APIs
var msg = { type: "message", text: document.getelementbyid("text").value, id: clientid, date: date.now() }; // send the msg object as a json-formatted string.
... document.getelementbyid("text").value = ""; } receiving messages from the server websockets is an event-driven api; when messages are received, a message event is sent to the websocket object.
...there are assorted types of data packets the client might receive, such as: login handshake message text user list updates the code that interprets these incoming messages might look like this: examplesocket.onmessage = function(event) { var f = document.getelementbyid("chatbox").contentdocument; var text = ""; var msg = json.parse(event.data); var time = new date(msg.date); var timestr = time.tolocaletimestring(); switch(msg.type) { case "id": clientid = msg.id; setusername(); break; case "username": text = "<b>user <em>" + msg.name + "</em> signed in at " + timestr + "</b><br>"; break; case "message": ...
... text = "(" + timestr + ") <b>" + msg.name + "</b>: " + msg.text + "<br>"; break; case "rejectusername": text = "<b>your username has been set to <em>" + msg.name + "</em> because the name you chose is in use.</b><br>" break; case "userlist": var ul = ""; for (i=0; i < msg.users.length; i++) { ul += msg.users[i] + "<br>"; } document.getelementbyid("userlistbox").innerhtml = ul; break; } if (text.length) { f.write(text); document.getelementbyid("chatbox").contentwindow.scrollbypages(1); } }; here we use json.parse() to convert the json object back into the original object, then examine and act upon its contents.

Cross-browser audio basics - Developer guides
</audio> you can grab the <audio> element like this: var myaudio = document.getelementbyid('my-audio'); alternatively, you can create a new element.
...le.ogg" type="audio/ogg"> <!-- place fallback here as <audio> supporting browsers will ignore it --> <p>download<a href="audiofile.mp3">audiofile.mp3</a></p> </audio> <!-- custom play and pause buttons --> <button id="play">play</button> <button id="pause">pause</button> next, we attach some functionality to the player using javascript: window.onload = function(){ var myaudio = document.getelementbyid('my-audio'); var play = document.getelementbyid('play'); var pause = document.getelementbyid('pause'); // associate functions with the 'onclick' events play.onclick = playaudio; pause.onclick = pauseaudio; function playaudio() { myaudio.play(); } function pauseaudio() { myaudio.pause(); } } media loading events above we have shown how you can create a very simple a...
...ause" style="display:none" >pause</button> </div> <div id="progress"> <div id="bar"></div> </div> styled like so: #controls { width: 80px; float: left; } #progress { margin-left: 80px; border: 1px solid black; } #bar { height: 20px; background-color: green; width: 0; } now let's wire this thing up with javascript: window.onload = function(){ var myaudio = document.getelementbyid('my-audio'); var play = document.getelementbyid('play'); var pause = document.getelementbyid('pause'); var loading = document.getelementbyid('loading'); var bar = document.getelementbyid('bar'); function displaycontrols() { loading.style.display = "none"; play.style.display = "block"; } // check that the media is ready before displaying the controls if (myaud...
... first of all, we apply a quick update to the progress bar css to display the hand pointer on hover: #progress { margin-left: 80px; border: 1px solid black; cursor: pointer; } then we add the code that detects the click and moves the 'playhead' to the correct position: var progress = document.getelementbyid('progress'); progress.addeventlistener('click', function(e) { // calculate the normalized position clicked var clickposition = (e.pagex - this.offsetleft) / this.offsetwidth; var clicktime = clickposition * myaudio.duration; // move the playhead to the correct position myaudio.currenttime = clicktime; }); buffering ok, we're getting there, but there is another piece of useful info...

Media buffering, seeking, and time ranges - Developer guides
this will work with <audio> or <video>; for now let's consider a simple audio example: <audio id="my-audio" controls src="music.mp3"> </audio> we can access these attributes like so: var myaudio = document.getelementbyid('my-audio'); var bufferedtimeranges = myaudio.buffered; timeranges object timeranges are a series of non-overlapping ranges of time, with start and stop times.
.../ returns 15 myaudio.buffered.end(1); // returns 19 to try out and visualize buffered time ranges we can write a little bit of html: <p> <audio id="my-audio" controls> <source src="music.mp3" type="audio/mpeg"> </audio> </p> <p> <canvas id="my-canvas" width="300" height="20"> </canvas> </p> and a little bit of javascript: window.onload = function(){ var myaudio = document.getelementbyid('my-audio'); var mycanvas = document.getelementbyid('my-canvas'); var context = mycanvas.getcontext('2d'); context.fillstyle = 'lightgray'; context.fillrect(0, 0, mycanvas.width, mycanvas.height); context.fillstyle = 'red'; context.strokestyle = 'white'; var inc = mycanvas.width / myaudio.duration; // display timeranges myaudio.addeventlistener('seeked', fu...
...300px; } #buffered-amount { display: block; height: 100%; background-color: #777; width: 0; } .progress { margin-top: -20px; height: 20px; position: relative; width: 300px; } #progress-amount { display: block; height: 100%; background-color: #595; width: 0; } and the following javascript provides our functionality: window.onload = function(){ var myaudio = document.getelementbyid('my-audio'); myaudio.addeventlistener('progress', function() { var duration = myaudio.duration; if (duration > 0) { for (var i = 0; i < myaudio.buffered.length; i++) { if (myaudio.buffered.start(myaudio.buffered.length - 1 - i) < myaudio.currenttime) { document.getelementbyid("buffered-amount").style.width = (myaudio.buffered.end(myaudio.buffered.leng...
...th - 1 - i) / duration) * 100 + "%"; break; } } } }); myaudio.addeventlistener('timeupdate', function() { var duration = myaudio.duration; if (duration > 0) { document.getelementbyid('progress-amount').style.width = ((myaudio.currenttime / duration)*100) + "%"; } }); } the progress event is fired as data is downloaded, this is a good event to react to if we want to display download or buffering progress.

Constraint validation - Developer guides
d-12345 or 12345" ], nl : [ '^(nl-)?\\d{4}\\s*([a-rt-z][a-z]|s[bce-rt-z])$', "nederland zips must have exactly 4 digits, followed by 2 letters except sa, sd and ss" ] }; // read the country id var country = document.getelementbyid("country").value; // get the npa field var zipfield = document.getelementbyid("zip"); // build the constraint checker var constraint = new regexp(constraints[country][0], ""); console.log(constraint); // check it!
... tell it zipfield.setcustomvalidity(""); } else { // the zip doesn't follow the constraint, we use the constraintapi to // give a message about the format required for this country zipfield.setcustomvalidity(constraints[country][1]); } } then we link it to the onchange event for the <select> and the oninput event for the <input>: window.onload = function () { document.getelementbyid("country").onchange = checkzip; document.getelementbyid("zip").oninput = checkzip; } you can see a live example of the postal code validation.
... here is the html part: <label for="fs">select a file smaller than 75 kb : </label> <input type="file" id="fs"> this displays: the javascript reads the file selected, uses the file.size() method to get its size, compares it to the (hard coded) limit, and calls the constraint api to inform the browser if there is a violation: function checkfilesize() { var fs = document.getelementbyid("fs"); var files = fs.files; // if there is (at least) one file selected if (files.length > 0) { if (files[0].size > 75 * 1024) { // check the constraint fs.setcustomvalidity("the selected file must not be larger than 75 kb"); return; } } // no custom constraint violation fs.setcustomvalidity(""); } finally we hook the method with the correct event: window.o...
...nload = function () { document.getelementbyid("fs").onchange = checkfilesize; } you can see a live example of the file size constraint validation.

Using templates and slots - Web Components
let's look at a trivial quick example: <template id="my-paragraph"> <p>my paragraph</p> </template> this won't appear in your page until you grab a reference to it with javascript and then append it to the dom, using something like the following: let template = document.getelementbyid('my-paragraph'); let templatecontent = template.content; document.body.appendchild(templatecontent); although trivial, you can already start to see how this could be useful.
...we'll call it <my-paragraph>: customelements.define('my-paragraph', class extends htmlelement { constructor() { super(); let template = document.getelementbyid('my-paragraph'); let templatecontent = template.content; const shadowroot = this.attachshadow({mode: 'open'}) .appendchild(templatecontent.clonenode(true)); } } ); the key point to note here is that we append a clone of the template content to the shadow root, created using the node.clonenode() method.
... customelements.define('element-details', class extends htmlelement { constructor() { super(); const template = document .getelementbyid('element-details-template') .content; const shadowroot = this.attachshadow({mode: 'open'}) .appendchild(template.clonenode(true)); } } ); using the <element-details> custom element with named slots now let’s take that <element-details> element and actually use it in our document: <element-details> <span slot="element-name">slot</span> <span slot="description"...
...echanism for holding client- side content that is not to be rendered when a page is loaded but may subsequently be instantiated during runtime using javascript.</span> </element-details> <script> customelements.define('element-details', class extends htmlelement { constructor() { super(); const template = document .getelementbyid('element-details-template') .content; const shadowroot = this.attachshadow({mode: 'open'}) .appendchild(template.clonenode(true)); } }) </script> </body> </html> ...

dev/panel - Archive of obsolete content
y-panel.html", onready: function() { this.postmessage("message from the add-on"); } }); // export the constructor exports.mypanel = mypanel; // create a new tool, initialized // with the new constructor const mytool = new tool({ panels: { mypanel: mypanel } }); in the panel document script: // my-panel.js window.addeventlistener("message", function(event) { var content = document.getelementbyid("content"); content.textcontent = event.data; }); note that at the moment you have to pass an array of ports into postmessage, even if you don't need to use them: // main.js // require the sdk modules const { panel } = require("dev/panel"); const { tool } = require("dev/toolbox"); const { class } = require("sdk/core/heritage"); const mypanel = class({ extends: panel, label: "my panel",...
... }, dispose: function() { this.debuggee = null; }, onready: function() { this.debuggee.start(); this.postmessage("port", [this.debuggee]); } }); // export the constructor exports.mypanel = mypanel; // create a new tool, initialized // with the new constructor const mytool = new tool({ panels: { mypanel: mypanel } }); in my-panel.js: // my-panel.js var content = document.getelementbyid("content"); window.addeventlistener("message", function(event) { var debuggee = event.ports[0]; console.log(debuggee); debuggee.onmessage = function(event) { content.textcontent = json.stringify(event.data); } debuggee.postmessage({ "to":"root", "type":"listtabs" }); }); if you do this, don't forget to call start() on the port before passing it over to the panel docum...
...like this: <html> <head> <meta charset="utf-8"> <link href="./my-panel.css"rel="stylesheet"></link> <script src="resource://sdk/dev/volcan.js"></script> </head> <body> <div id = "content"></div> </body> <script src="./my-panel.js"></script> </html> here's a script that uses volcan.js to get the selected tab and display its url: // my-panel.js var content = document.getelementbyid("content"); window.addeventlistener("message", function(event) { var debuggee = event.ports[0]; volcan.connect(debuggee).

Canvas code snippets - Archive of obsolete content
function canvas2dcontext(canvas) { if (typeof canvas === 'string') { canvas = document.getelementbyid(canvas); } if (!(this instanceof canvas2dcontext)) { return new canvas2dcontext(canvas); } this.context = this.ctx = canvas.getcontext('2d'); if (!canvas2dcontext.prototype.arc) { canvas2dcontext.setup.call(this, this.ctx); } } canvas2dcontext.setup = function() { var methods = ['arc', 'arcto', 'beginpath', 'beziercurveto', 'clearrect', 'clip', 'closepath', 'drawimage', ...
...ethods) { let method = m; canvas2dcontext.prototype[method] = function() { return this.ctx[method].apply(this.ctx, arguments); }; } for (let p of props) { let prop = p; canvas2dcontext.prototype[prop] = function(value) { if (value === undefined) return this.ctx[prop]; this.ctx[prop] = value; return this; }; } }; var canvas = document.getelementbyid('canvas'); // use context to get access to underlying context var ctx = canvas2dcontext(canvas) .strokestyle('rgb(30, 110, 210)') .transform(10, 3, 4, 5, 1, 0) .strokerect(2, 10, 15, 20) .context; // use property name as a function (but without arguments) to get the value var strokestyle = canvas2dcontext(canvas) .strokestyle('rgb(50, 110, 210)') .strokestyle(); code usable only f...
...add a listener to the // frame's onload event iframe.addeventlistener('load', this.remotepageloaded, true); //append to the end of the page window.document.body.appendchild(iframe); return; }; remotecanvas.prototype.remotepageloaded = function() { // look back up the iframe by id var ldrframe = document.getelementbyid('test-iframe'); // get a reference to the window object you need for the canvas // drawwindow method var remotewindow = ldrframe.contentwindow; //draw canvas var canvas = document.createelement('canvas'); canvas.style.width = remotecanvas.canvas_width + 'px'; canvas.style.height = remotecanvas.canvas_height + 'px'; canvas.width = remotecanvas.canvas_width; can...

Using XML Data Islands in Mozilla - Archive of obsolete content
d like this: <script id="purchase-order" type="application/xml"> <purchaseorder xmlns="http://example.mozilla.org/purchaseorderml"> <lineitem> <name>line item 1</name> <price>1.25</price> </lineitem> <lineitem> <name>line item 2</name> <price>2.48</price> </lineitem> </purchaseorder> </script> the xml source text can then be retrieved like this: var ordersource = document.getelementbyid("purchase-order").textcontent; the xml source text can be parsed into a dom tree using the domparser api: var parser = new domparser(); var doc = parser.parsefromstring(ordersource, "application/xml"); the html5 data block-based way shown here works in firefox, opera, webkit-based browsers such as chrome and safari, and ie9 while ie's xml data islands work only in ie.
...<title>xml data block demo</title> <script id="purchase-order" type="application/xml"> <purchaseorder xmlns="http://example.mozilla.org/purchaseorderml"> <lineitem> <name>line item 1</name> <price>1.25</price> </lineitem> <lineitem> <name>line item 2</name> <price>2.48</price> </lineitem> </purchaseorder> </script> <script> function rundemo() { var ordersource = document.getelementbyid("purchase-order").textcontent; var parser = new domparser(); var doc = parser.parsefromstring(ordersource, "application/xml"); var lineitems = doc.getelementsbytagnamens("http://example.mozilla.org/purchaseorderml", "lineitem"); var firstprice = lineitems[0].getelementsbytagnamens("http://example.mozilla.org/purchaseorderml", "price")[0].textcontent; document.body.textcontent = "the pur...
...for this demo, you must create an external document called purchase_order.xml: <!doctype html> <html> <head> <title>xml data block demo</title> <script> function rundemo() { var doc = document.getelementbyid("purchase-order").contentdocument; var lineitems = doc.getelementsbytagnamens("http://example.mozilla.org/purchaseorderml", "lineitem"); var firstprice = lineitems[0].getelementsbytagnamens("http://example.mozilla.org/purchaseorderml", "price")[0].textcontent; document.getelementbyid("output-box").textcontent = "the purchase order contains " + lineitems.length + " line items.

Introducing the Audio API extension - Archive of obsolete content
xample</title> </head> <body> <audio id="audio-element" src="song.ogg" controls="true" style="width: 512px;"> </audio> <script> function loadedmetadata() { channels = audio.mozchannels; rate = audio.mozsamplerate; framebufferlength = audio.mozframebufferlength; } var audio = document.getelementbyid('audio-element'); audio.addeventlistener('loadedmetadata', loadedmetadata, false); </script> </body> </html> the mozaudioavailable event as the audio is played, sample data is made available to the audio layer and the audio buffer (size defined in mozframebufferlength) gets filled with those samples.
...; rate = audio.mozsamplerate; framebufferlength = audio.mozframebufferlength; } function audioavailable(event) { var framebuffer = event.framebuffer; var t = event.time; var text = "samples at: " + t + "\n"; text += framebuffer[0] + " " + framebuffer[1]; raw.innerhtml = text; } var raw = document.getelementbyid('raw'); var audio = document.getelementbyid('audio-element'); audio.addeventlistener('mozaudioavailable', audioavailable, false); audio.addeventlistener('loadedmetadata', loadedmetadata, false); </script> </body> </html> creating an audio stream it is also possible to create and setup an <audio> element for raw writing from script (i.e., without a src attribute).
... <audio id="a1" src="song.ogg" controls> </audio> <script> var a1 = document.getelementbyid('a1'), a2 = new audio(), buffers = []; function loadedmetadata() { // mute a1 audio.

jspage - Archive of obsolete content
b){if(browser.engine.trident&&b){["name","type","checked"].each(function(c){if(!b[c]){return;}a+=" "+c+'="'+b[c]+'"'; if(c!="checked"){delete b[c];}});a="<"+a+">";}return document.id(this.createelement(a)).set(b);},newtextnode:function(a){return this.createtextnode(a); },getdocument:function(){return this;},getwindow:function(){return this.window;},id:(function(){var a={string:function(d,c,b){d=b.getelementbyid(d);return(d)?a.element(d,c):null; },element:function(b,e){$uid(b);if(!e&&!b.$family&&!(/^object|embed$/i).test(b.tagname)){var c=element.prototype;for(var d in c){b[d]=c[d];}}return b;},object:function(c,d,b){if(c.toelement){return a.element(c.toelement(b),d); }return null;}};a.textnode=a.whitespace=a.window=a.document=$arguments(0);return function(c,e,d){if(c&&c.$family&&c.uid){return c;}var b=$...
...nt:function(l,m){return j(this,"parentnode",null,l,false,m);},getparents:function(l,m){return j(this,"parentnode",null,l,true,m);},getsiblings:function(l,m){return this.getparent().getchildren(l,m).erase(this); },getchildren:function(l,m){return j(this,"nextsibling","firstchild",l,true,m);},getwindow:function(){return this.ownerdocument.window;},getdocument:function(){return this.ownerdocument; },getelementbyid:function(o,n){var m=this.ownerdocument.getelementbyid(o);if(!m){return null;}for(var l=m.parentnode;l!=this;l=l.parentnode){if(!l){return null; }}return document.id(m,n);},getselected:function(){return new elements($a(this.options).filter(function(l){return l.selected;}));},getcomputedstyle:function(m){if(this.currentstyle){return this.currentstyle[m.camelcase()]; }var l=this.getdocument().defaul...
...f(!selectors.filters.byclass(f,g)){return false;}}}if(c.attributes){for(d=c.attributes.length; d--;d){var b=c.attributes[d];if(!selectors.filters.byattribute(f,b.name,b.operator,b.value)){return false;}}}if(c.pseudos){for(d=c.pseudos.length;d--;d){var a=c.pseudos[d]; if(!selectors.filters.bypseudo(f,a.parser,a.argument,e)){return false;}}}return true;},getbytagandid:function(b,a,d){if(d){var c=(b.getelementbyid)?b.getelementbyid(d,true):element.getelementbyid(b,d,true); return(c&&selectors.filters.bytag(c,a))?[c]:[];}else{return b.getelementsbytagname(a);}},search:function(o,h,t){var b=[];var c=h.trim().replace(selectors.regexps.splitter,function(k,j,i){b.push(j); return":)"+i;}).split(":)");var p,e,a;for(var z=0,v=c.length;z<v;z++){var y=c[z];if(z==0&&selectors.regexps.quick.test(y)){p=o.getelementsbyt...

Dynamically modifying XUL-based user interface - Archive of obsolete content
the most well known dom method is probably document.getelementbyid(), which returns an element, given its id.
...var element = document.getelementbyid("someelement"); while(element.haschildnodes()){ element.removechild(element.firstchild); } inserting menu items to a menu this example adds two new menu items to a <menupopup>: to the start and to the end of it.
... function createmenuitem(alabel) { const xul_ns = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"; var item = document.createelementns(xul_ns, "menuitem"); // create a new xul menuitem item.setattribute("label", alabel); return item; } var popup = document.getelementbyid("mypopup"); // a <menupopup> element var first = createmenuitem("first item"); var last = createmenuitem("last item"); popup.insertbefore(first, popup.firstchild); popup.appendchild(last); you can also use appendchild() and insertbefore() to move existing elements.

Introduction to XUL - Archive of obsolete content
<html:script type="application/javascript"> // dialog initialization code function initwindow() { var checkbox = document.getelementbyid("remember"); if (checkbox) checkbox.checked = true; } </html:script> javascript can be referenced as in html documents: as onclick handlers and the like.
... xuldocument xuldocument extends document in a fashion similar to htmldocument's extension interface xuldocument : document { element getelementbyid(in domstring id); nodelist getelementsbyattribute(in domstring name, in domstring value); }; getelementbyid works like html's getelementbyid.
...however in practice, most nodes in xul have these identifiers, which enable the nodes to be retrieved easily using the aom's getelementbyid method.

ContextMenus - Archive of obsolete content
function checkcontextmenu(event) { if (event.target.localname == "textbox") event.preventdefault(); } function init() { var container = document.getelementbyid("container"); container.addeventlistener("contextmenu", checkcontextmenu, true); } the 'checkcontextmenu' function checks to see if the textbox was the target of the context menu and, if so, cancels the event using the preventdefault method.
... <script> function showhidedeleteitem() { var deleteitem = document.getelementbyid("delete"); var rows = document.getelementbyid("rows"); deleteitem.hidden = (rows.childnodes.length == 0); } </script> <menupopup id="inssel-menu" onpopupshowing="showhidedeleteitem()"> <menuitem label="insert"/> <menuitem id="delete" label="delete"/> </menupopup> in this example, the showhidedeleteitem function is called when the popupshowing event is fired.
... var element = aevent.target.triggernode; var isimage = (element instanceof components.interfaces.nsiimageloadingcontent && element.currenturi); document.getelementbyid("enlarge").hidden = !isimage; document.getelementbyid("details").hidden = !isimage; } </script> <menupopup id="contentareacontextmenu" onpopupshowing="showhideitems(event)"> <menuitem label="copy"/> <menuitem id="enlarge" label="enlarge image"/> <menuitem id="details" label="image details"/> </menupopup> <browser src="http://www.mozilla.org" context="contentareacontextmenu"/> when the...

MenuModification - Archive of obsolete content
<script> function addtomenu() { var menu = document.getelementbyid("edit-menu"); menu.appenditem("insert", "insert"); } </script> <menu id="edit-menu"/> <button label="add" oncommand="addtomenu()"/> in this example, the addtomenu function is called when the button is pressed.
... <script> function addsubmenu() { var popup = document.getelementbyid("file-popup"); var newmenu = document.createelement("menu"); popup.appendchild(newmenu); newmenu.label = "new"; newmenu.appenditem("document", "doc"); newmenu.appenditem("image", "image"); } </script> <menu label="file" onpopupshowing="addsubmenu()"> <menupopup id="file-popup"/> </menu>.
... <script> function addsubmenu() { var popup = document.getelementbyid("file-popup"); if (popup.haschildnodes()) return; var newmenu = document.createelement("menu"); popup.appendchild(newmenu); newmenu.label = "new"; newmenu.appenditem("document", "doc"); newmenu.appenditem("image", "image"); } </script> the haschildnodes method may be used to check if a node has any children.

Sorting and filtering a custom tree view - Archive of obsolete content
k="sort(this)" class="sortdirectionindicator"/> <splitter class="tree-splitter"/> <treecol id="weapon" label="weapon" flex="1" persist="width ordinal hidden" onclick="sort(this)" class="sortdirectionindicator"/> </treecols> <treechildren id="tree-children"/> </tree> </window> sort.js var table = null; var data = null; var tree; var filtertext = ""; function init() { tree = document.getelementbyid("tree"); loadtable(); } //this function is called every time the tree is sorted, filtered, or reloaded function loadtable() { //remember scroll position.
..."ascending" : "descending"); tree.setattribute("sortresource", columnname); tree.view = new treeview(table); //set the appropriate attributes to show to indicator var cols = tree.getelementsbytagname("treecol"); for (var i = 0; i < cols.length; i++) { cols[i].removeattribute("sortdirection"); } document.getelementbyid(columnname).setattribute("sortdirection", order == 1 ?
... { return o.tolowercase(); } return o; } function gettopvisiblerow() { return tree.treeboxobject.getfirstvisiblerow(); } function settopvisiblerow(topvisiblerow) { return tree.treeboxobject.scrolltorow(topvisiblerow); } function inputfilter(event) { //do this now rather than doing it at every comparison var value = prepareforcomparison(event.target.value); setfilter(value); document.getelementbyid("clearfilter").disabled = value.length == 0; } function clearfilter() { document.getelementbyid("clearfilter").disabled = true; var filterelement = document.getelementbyid("filter"); filterelement.focus(); filterelement.value = ""; setfilter(""); } function setfilter(text) { filtertext = text; loadtable(); } ...

Commands - Archive of obsolete content
example: toggling command disabled example 2 : source view <command id="cmd_openhelp" oncommand="alert('help');"/> <button label="help" command="cmd_openhelp"/> <button label="more help" command="cmd_openhelp"/> <button label="disable" oncommand="document.getelementbyid('cmd_openhelp').setattribute('disabled','true');"/> <button label="enable" oncommand="document.getelementbyid('cmd_openhelp').removeattribute('disabled');"/> in this example, both buttons use the same command.
... <window id="controller-example" title="controller example" onload="init();" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> function init() { var list = document.getelementbyid("thelist"); var listcontroller = { supportscommand : function(cmd){ return (cmd == "cmd_delete"); }, iscommandenabled : function(cmd){ if (cmd == "cmd_delete") return (list.selecteditem != null); return false; }, docommand : function(cmd){ list.removeitemat(list.selectedindex); }, onevent : function(evt){ } }; list.controllers.appendcontroller(lis...
... var tboxcontroller = { supportscommand : function(cmd){ return (cmd == "cmd_paste"); }, iscommandenabled : function(cmd){ return false; }, docommand : function(cmd){ }, onevent : function(evt){ } }; document.getelementbyid("tbox").controllers.insertcontrollerat(0,tboxcontroller); in this example, we insert the controller at index 0, which means before any others.

Focus and Selection - Archive of obsolete content
example 2 : source view <script> function displayfocus(){ var elem=document.getelementbyid('sbar'); elem.setattribute('value','enter your phone number.'); } </script> <textbox id="tbox1"/> <textbox id="tbox2" onfocus="displayfocus();"/> <description id="sbar" value=""/> the focus event, when it occurs, will call the displayfocus function.
...example 3 : source view <window id="focus-example" title="focus example" onload="init();" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> function init(){ addeventlistener("focus",setfocusedelement,true); } function setfocusedelement(){ var focused = document.commanddispatcher.focusedelement; document.getelementbyid("focused").value = focused.tagname; } </script> <hbox> <label control="username" value="user name:"/> <textbox id="username"/> </hbox> <button label="hello"/> <checkbox label="remember this decision"/> <label id="focused" value="-no focus-"/> </window> in this example, a focus event handler is attached the window.
...the following example demonstrates this: example 5 : source view <textbox id="addr"/> <button label="focus" oncommand="document.getelementbyid('addr').focus()"/> or, you can use the methods advancefocus and rewindfocus on the command dispatcher.

Tree Box Objects - Archive of obsolete content
example 1 : source view <script> function doscroll(){ var value = document.getelementbyid("tbox").value; var tree = document.getelementbyid("thetree"); var boxobject = tree.boxobject; boxobject.queryinterface(components.interfaces.nsitreeboxobject); boxobject.scrolltorow(value); } </script> <tree id="thetree" rows="4"> <treecols> <treecol id="row" label="row" primary="true" flex="1"/> </treecols> <treechildren> <treeitem label="row 0"/> <treeitem label="row...
... example 2 : source view <script> function updatefields(event){ var row = {}, column = {}, part = {}; var tree = document.getelementbyid("thetree"); var boxobject = tree.boxobject; boxobject.queryinterface(components.interfaces.nsitreeboxobject); boxobject.getcellat(event.clientx, event.clienty, row, column, part); if (column.value && typeof column.value != "string") column.value = column.value.id; document.getelementbyid("row").value = row.value; document.getelementbyid("column").value = column.value; documen...
...t.getelementbyid("part").value = part.value; } </script> <tree id="thetree" flex="1" onmousemove="updatefields(event);"> <treecols> <treecol id="utensil" label="utensil" primary="true" flex="1"/> <treecol id="count" label="count" flex="1"/> </treecols> <treechildren> <treeitem> <treerow> <treecell label="fork"/> <treecell label="5"/> </treerow> </treeitem> <treeitem> <treerow> <treecell label="knife"/> <treecell label="2"/> </treerow> </treeitem> <treeitem> <treerow> <treecell label="spoon"/> <treecell label="8"/> </treerow> </treeitem> </treechildren> </tree> <label value="row:"/> <label id="row"/> <label value="column:"/> <label id="column"/> <label value="child type:"/> <labe...

Using the Editor from XUL - Archive of obsolete content
having an id attribute, id="content-frame", allows us to find this element with document.getelementbyid("content-frame"), and to style it from css.
...we could either pass document.getelementbyid("content-frame") or window._content here.
...we get the url to load from the args element, then kick off the load: var url = document.getelementbyid("args").getattribute("value"); editorshell.loadurl(url); loading the document in the <iframe> of course happens asynchronously, so we need to know when we have a document that we can start editing.

Extentsions FAQ - Archive of obsolete content
"); var replaceme = document.getelementbyid("replaceme"); replaceme.parentnode.replacechild(newnode, replaceme); is it possible to place an image in the window that can be moved to anywhere in the window, and always remain on top of everything else?(similiar to using position:absolute and-index:100000 in html) you can almost do this with a stack: <window ...> <stack flex="1"> <image top="40" left="80"/> <vbox> ...
... //setting the state document.getelementbyid("toolbar-button").setattribute("toolbar-button", "on"); //or document.getelementbyid("toolbar-button").setattribute("toolbar-button","off"); //css #myexten-toolbar-button[myexten-toolbar-button="on"] { list-style-image: url("chrome://myexten/skin/toolbar-button.png"); -moz-image-region: rect(0px 24px 24px 0px);} #myexten-toolbar-button[myexten-toolbar-button="off"] { list-style-image:...
...is should work: var ci = components.interfaces; var toplevelwindow = window.queryinterface(ci.nsiinterfacerequestor) .getinterface(ci.nsiwebnavigation) .queryinterface(ci.nsidocshelltreeitem) .roottreeitem .queryinterface(ci.nsiinterfacerequestor) .getinterface(ci.nsidomwindow) .queryinterface(ci.nsidomchromewindow); var sidebar = toplevelwindow.document.getelementbyid("sidebar"); alert(sidebar.contentdocument); is there anyone successfully using dojo in a firefox extension and where to fine sample codes?

Developing cross-browser and cross-platform pages - Archive of obsolete content
function hideelement(id_attribute_value) { if (document.getelementbyid && document.getelementbyid(id_attribute_value) && document.getelementbyid(id_attribute_value).style ) { document.getelementbyid(id_attribute_value).style.visibility = "hidden"; }; } // example: // <button type="button" onclick="hideelement('d1');">hide div</button> // <div id="d1">some text</div> these repeated calls to document.getelementbyid are not the most efficient way ...
... the top-level if clause looks to see if there is support for a method called getelementbyid on the document object, which is the one of the most basic levels of support for the dom in a browser.
... if there is, the code sees if document.getelementbyid(id_attribute_value) returns a reference to an existing element, which it then checks for a style object.

Client-side form validation - Learn web development
we'll start with some simple html (feel free to put this in a blank html file; use a fresh copy of fruit-start.html as a basis, if you like): <form> <label for="mail">i would like you to provide me with an e-mail address:</label> <input type="email" id="mail" name="mail"> <button>submit</button> </form> and add the following javascript to the page: const email = document.getelementbyid("mail"); email.addeventlistener("input", function (event) { if (email.validity.typemismatch) { email.setcustomvalidity("i am expecting an e-mail address!"); } else { email.setcustomvalidity(""); } }); here we store a reference to the email input, then add an event listener to it that runs the contained code each time the value inside the input is changed.
...const form = document.getelementsbytagname('form')[0]; const email = document.getelementbyid('mail'); const emailerror = document.queryselector('#mail + span.error'); email.addeventlistener('input', function (event) { // each time the user types something, we check if the // form fields are valid.
... // there are fewer ways to pick a dom node with legacy browsers const form = document.getelementsbytagname('form')[0]; const email = document.getelementbyid('mail'); // the following is a trick to reach the next sibling element node in the dom // this is dangerous because you can easily build an infinite loop.

Sending forms through JavaScript - Learn web development
const form = document.getelementbyid( "myform" ); // ...and take over its submit event.
...window.addeventlistener( 'load', function () { // these variables are used to store the form data const text = document.getelementbyid( "thetext" ); const file = { dom : document.getelementbyid( "thefile" ), binary : null }; // use the filereader api to access file content const reader = new filereader(); // because filereader is asynchronous, store its // result when it finishes to read the file reader.addeventlistener( "load", function () { file.binary = reader.result; } ); // at...
... const form = document.getelementbyid( "theform" ); // ...to take over the submit event form.addeventlistener( 'submit', function ( event ) { event.preventdefault(); senddata(); } ); } ); here's the live result: conclusion depending on the browser and the type of data you are dealing with, sending form data through javascript can be easy or difficult.

Advanced text formatting - Learn web development
t brown color.</textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); const output = document.queryselector('.output'); const code = textarea.value; const userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solution...
...hinking.)</p> </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); const output = document.queryselector('.output'); const code = textarea.value; const userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solution...
...ing work.</p> </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); const output = document.queryselector('.output'); const code = textarea.value; const userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solution...

Getting started with HTML - Learn web development
v class="controls"> <input id="reset" type="button" value="reset" /> <input id="solution" type="button" value="show solution" /> </div> html { font-family: 'open sans light',helvetica,arial,sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...
...site.&lt;/p&gt; </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...
...buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h1 { color: blue; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } img { max-width: 100%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...

Useful string methods - Learn web development
item); } } </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...
...listitem); } </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...
...istitem); } </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...

Getting started with React - Learn web development
this file is the entry point for our app, and it initially looks like this: import react from 'react'; import reactdom from 'react-dom'; import './index.css'; import app from './app'; import * as serviceworker from './serviceworker'; reactdom.render(<app />, document.getelementbyid('root')); // if you want your app to work offline and load faster, you can change // unregister() to register() below.
... your final index.js file should look like this: import react from 'react'; import reactdom from 'react-dom'; import './index.css'; import app from './app'; reactdom.render(<app />, document.getelementbyid('root')); variables and props next, we'll use a few of our javascript skills to get a bit more comfortable editing components and working with data in react.
...when you are done, your code should look something like this: reactdom.render(<app subject="clarice" />, document.getelementbyid('root')); back in app.js, let's revisit the app function itself, which reads like this (with the return statement shortened for brevity): function app() { const subject = "react"; return ( // return statement ); } change the signature of the app function so that it accepts props as a parameter, and delete the subject const.

Mozilla DOM Hacking Guide
for example, when we ask for |document.getelementbyid("myid");|, xpconnect will find that |document| is a property of the window object, so it will look on the interface nsidomwindow, and it will find the getdocument() method.
...so xpconnect will then try to find a method named getelementbyid() on the nsidomdocument interface.
..."interface flattening is the ability to call methods on an object regardless of the interface it was defined on." for example, when we have the document object in javascript, we can call indistinctly document.getelementbyid(), or document.addeventlistener(), although they are defined on two different interfaces (domdocument and domeventtarget.

Mozilla Web Developer FAQ
you should not rely on mozilla’s document.all support on new pages.) the method document.getelementbyid() can be used instead.
...the correct way to access an element by id is to call the document.getelementbyid() method with the id as a string as the argument.
...for example, the existence of document.getelementbyid() can be checked as follows: if(document.getelementbyid) { /* code that uses document.getelementbyid() */ } why doesn’t mozilla display my alt tooltips?

Components.utils.exportFunction
nges to the argument that are made in the exported function will affect the original object that was passed in: // privileged scope: for example, a content script function changemyname(user) { user.name = "bill"; } exportfunction(changemyname, contentwindow, { defineas: "changemyname" }); // less-privileged scope: for example, a page script var user = {name: "jim"}; var test = document.getelementbyid("test"); test.addeventlistener("click", function() { console.log(user.name); // "jim" window.changemyname(user); console.log(user.name); // "bill" }, false); note that this is subject to the normal rules of xrays: for example, an expando property added to a dom node will not be visible in the original object.
...e xrays: // privileged scope: for example, a content script function loguser(user) { // console.log(user.getuser()); // error console.log(user.wrappedjsobject.getuser()); // "bill" } exportfunction(loguser, contentwindow, { defineas: "loguser" }); // less-privileged scope: for example, a page script var user = {getuser: function() {return "bill";}} var test = document.getelementbyid("test"); test.addeventlistener("click", function() { window.loguser(user); }, false); passing functions as arguments if functions are given as arguments, these are also passed as xrays.
...ng callbacks into the exported function just works, making the allowcallbacks option redundant: // privileged scope: for example, a content script function loguser(getuser) { console.log(getuser()); // "bill" } exportfunction(loguser, unsafewindow, { defineas: "loguser" }); // less-privileged scope: for example, a page script function getuser() { return "bill"; } var test = document.getelementbyid("test"); test.addeventlistener("click", function() { window.loguser(getuser); }, false); cross-origin checking when the exported function is called each argument, including this, is checked to make sure that the caller subsumes that argument.

Working with windows in chrome code
note however, that the open() call returns before the window is fully loaded, so some calls, like win.document.getelementbyid() will fail.
...to access the elements and variables inside the sidebar, you need to use document.getelementbyid("sidebar").contentdocument or .contentwindow, like when accessing content documents.
..., {status: "reading remote data", maxprogress: 50, progress: 10} ); progress.xul: <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <window onload="onload();" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script><![cdata[ var gstatus, gprogressmeter; var maxprogress = 100; function onload() { gstatus = document.getelementbyid("status"); gprogressmeter = document.getelementbyid("progressmeter"); if("arguments" in window && window.arguments.length > 0) { maxprogress = window.arguments[0].maxprogress; setprogress(window.arguments[0].progress); setstatus(window.arguments[0].status); } } function setprogress(value) { gprogressmeter.value = 100 * value / maxprogress; } function setstatus(text) { gst...

Using dynamic styling information - Web APIs
<html> <head> <title>simple style example</title> <script type="text/javascript"> function alterstyle(elem) { elem.style.background = 'green'; } function resetstyle(elemid) { elem = document.getelementbyid(elemid); elem.style.background = 'white'; } </script> <style type="text/css"> #p1 { border: solid blue 2px; } </style> </head> <body> <!-- passes a reference to the element's object as parameter 'this'.
... more important than the two properties noted here is the use of the style object to set individual style properties on an element: <!doctype html> <html> <head> <title>style property example</title> <link rel="stylesheet" href="example.css" type="text/css"> <script type="text/javascript"> function stilo() { document.getelementbyid('d').style.color = 'orange'; } function resetstyle() { document.getelementbyid('d').style.color = 'black'; } </script> </head> <body> <div id="d" class="thunder">thunder</div> <button onclick="stilo()">click here to change text color</button> <button onclick="resetstyle()">reset text color</button> </body> </html> the media and type of the style may or may not b...
... var el = document.getelementbyid('some-element'); el.setattribute('style', 'background-color:darkblue;'); be aware, however, that setattribute removes all other style properties that may already have been defined in the element's style object.

CanvasRenderingContext2D.stroke() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.rect(10, 10, 150, 100); ctx.stroke(); result re-stroking paths typically, you'll want to call beginpath() for each new thing you want to stroke.
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // first sub-path ctx.linewidth = 26; ctx.strokestyle = 'orange'; ctx.moveto(20, 20); ctx.lineto(160, 20); ctx.stroke(); // second sub-path ctx.linewidth = 14; ctx.strokestyle = 'green'; ctx.moveto(20, 80); ctx.lineto(220, 80); ctx.stroke(); // third sub-path ctx.linewidth = 4; ctx.strokestyle = 'pink'; ctx.moveto(20, 140); ctx.lineto(280, 140); ctx.stroke(); result strokin...
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.linewidth = 16; ctx.strokestyle = 'red'; // stroke on top of fill ctx.beginpath(); ctx.rect(25, 25, 100, 100); ctx.fill(); ctx.stroke(); // fill on top of stroke ctx.beginpath(); ctx.rect(175, 25, 100, 100); ctx.stroke(); ctx.fill(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.stroke'...

Document.getElementsByClassName() - Web APIs
examples get all elements that have a class of 'test': document.getelementsbyclassname('test') get all elements that have both the 'red' and 'test' classes: document.getelementsbyclassname('red test') get all elements that have a class of 'test', inside of an element that has the id of 'main': document.getelementbyid('main').getelementsbyclassname('test') get the first element with a class of 'test', or undefined if there is no matching element: document.getelementsbyclassname('test')[0] we can also use methods of array.prototype on any htmlcollection by passing the htmlcollection as the method's this value.
... <html> <body> <div id="parent-id"> <p>hello world 1</p> <p class="test">hello world 2</p> <p>hello world 3</p> <p>hello world 4</p> </div> <script> var parentdom = document.getelementbyid("parent-id"); var test = parentdom.getelementsbyclassname("test"); // a list of matching elements, *not* the element itself console.log(test); //htmlcollection[1] var testtarget = parentdom.getelementsbyclassname("test")[0]; // the first element, as we wanted console.log(testtarget); //<p class="test">hello world 2</p> </script> </body> </html> multiple clas...
...len; i=i+1|0) { result += "\n " + allorangejuicebyclass[i].textcontent; } // queryselector only selects full complete matches var allorangejuicequery = document.queryselectorall('.orange.juice'); result += "\n\ndocument.queryselectorall('.orange.juice')"; for (var i=0, len=allorangejuicequery.length|0; i<len; i=i+1|0) { result += "\n " + allorangejuicequery[i].textcontent; } document.getelementbyid("resultarea").value = result; result specifications specification status comment domthe definition of 'document.getelementsbyclassname' in that specification.

Element: fullscreenchange event - Web APIs
html <h1>fullscreenchange event example</h1> <div id="fullscreen-div"> <button id="toggle-fullscreen">toggle fullscreen mode</button> </div> javascript document.getelementbyid('fullscreen-div').addeventlistener('fullscreenchange', (event) => { // document.fullscreenelement will point to the element that // is in fullscreen mode if there is one.
... if (document.fullscreenelement) { console.log(`element: ${document.fullscreenelement.id} entered fullscreen mode.`); } else { console.log('leaving full-screen mode.'); } }); document.getelementbyid('toggle-fullscreen').addeventlistener('click', (event) => { if (document.fullscreenelement) { // exitfullscreen is only available on the document object.
... document.exitfullscreen(); } else { document.getelementbyid('fullscreen-div').requestfullscreen(); } }); specifications specification status fullscreen api living standard ...

Using the Gamepad API - Web APIs
var gamepadinfo = document.getelementbyid("gamepad-info"); var ball = document.getelementbyid("ball"); var start; var a = 0; var b = 0; next we use the gamepadconnected event to check for a gamepad being connected.
...; a.classname = "axes"; for (var i = 0; i < gamepad.axes.length; i++) { var p = document.createelement("progress"); p.classname = "axis"; //p.id = "a" + i; p.setattribute("max", "2"); p.setattribute("value", "1"); p.innerhtml = i; a.appendchild(p); } d.appendchild(a); // see https://github.com/luser/gamepadtest/blob/master/index.html var start = document.getelementbyid("start"); if (start) { start.style.display = "none"; } document.body.appendchild(d); requestanimationframe(updatestatus); } function disconnecthandler(e) { removegamepad(e.gamepad); } function removegamepad(gamepad) { var d = document.getelementbyid("controller" + gamepad.index); document.body.removechild(d); delete controllers[gamepad.index]; } function updatestatus() { ...
... if (!haveevents) { scangamepads(); } var i = 0; var j; for (j in controllers) { var controller = controllers[j]; var d = document.getelementbyid("controller" + j); var buttons = d.getelementsbyclassname("button"); for (i = 0; i < controller.buttons.length; i++) { var b = buttons[i]; var val = controller.buttons[i]; var pressed = val == 1.0; if (typeof(val) == "object") { pressed = val.pressed; val = val.value; } var pct = math.round(val * 100) + "%"; b.style.backgroundsize = pct + " " + pct; if (pressed) { b.classname = "button pressed"; } else { b.classname = "button"; } } var axes = d.getelementsbyclassname("axis"); for (i = 0; i < controller.axes.length; i++) { ...

HTMLCanvasElement.toBlob() - Web APIs
var canvas = document.getelementbyid('canvas'); canvas.toblob(function(blob) { var newimg = document.createelement('img'), url = url.createobjecturl(blob); newimg.onload = function() { // no longer need to read the blob so it's revoked url.revokeobjecturl(url); }; newimg.src = url; document.body.appendchild(newimg); }); note that here we're creating a png image; if you add a second parameter to the toblo...
... var canvas = document.getelementbyid('canvas'); var d = canvas.width; ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(d / 2, 0); ctx.lineto(d, d); ctx.lineto(0, d); ctx.closepath(); ctx.fillstyle = 'yellow'; ctx.fill(); function blobcallback(iconname) { return function(b) { var a = document.createelement('a'); a.textcontent = 'download'; document.body.appendchild(a); a.style.display = 'block'; a.dow...
... var canvas = document.getelementbyid('canvas'); var d = canvas.width; ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(d / 2, 0); ctx.lineto(d, d); ctx.lineto(0, d); ctx.closepath(); ctx.fillstyle = 'yellow'; ctx.fill(); function blobcallback(iconname) { return function(b) { var r = new filereader(); r.onloadend = function () { // r.result contains the arraybuffer.

Using microtasks in JavaScript with queueMicrotask() - Web APIs
let logelem = document.getelementbyid("log"); let log = s => logelem.innerhtml += s + "<br>"; in the following code, we see a call to queuemicrotask() used to schedule a microtask to run.
... let logelem = document.getelementbyid("log"); let log = s => logelem.innerhtml += s + "<br>"; in the following code, we see a call to queuemicrotask() used to schedule a microtask to run.
... let logelem = document.getelementbyid("log"); let log = s => logelem.innerhtml += s + "<br>"; the main program code follows.

HTML Drag and Drop API - Web APIs
uires adding the draggable attribute and the ondragstart global event handler, as shown in the following code sample: <script> function dragstart_handler(ev) { // add the target element's id to the data transfer object ev.datatransfer.setdata("text/plain", ev.target.id); } window.addeventlistener('domcontentloaded', () => { // get the element by id const element = document.getelementbyid("p1"); // add the ondragstart event listener element.addeventlistener("dragstart", dragstart_handler); }); </script> <p id="p1" draggable="true">this element is draggable.</p> for more information, see: draggable attribute reference drag operations guide define the drag's data the application is free to include any number of data items in a drag operation.
... <script> function dragover_handler(ev) { ev.preventdefault(); ev.datatransfer.dropeffect = "move"; } function drop_handler(ev) { ev.preventdefault(); // get the id of the target and add the moved element to the target's dom const data = ev.datatransfer.getdata("text/plain"); ev.target.appendchild(document.getelementbyid(data)); } </script> <p id="target" ondrop="drop_handler(event)" ondragover="dragover_handler(event)">drop zone</p> note that each handler calls preventdefault() to prevent additional event processing for this event (such as touch events or pointer events).
...fer.setdata("application/my-app", ev.target.id); ev.datatransfer.dropeffect = "move"; } function dragover_handler(ev) { ev.preventdefault(); ev.datatransfer.dropeffect = "move" } function drop_handler(ev) { ev.preventdefault(); // get the id of the target and add the moved element to the target's dom const data = ev.datatransfer.getdata("application/my-app"); ev.target.appendchild(document.getelementbyid(data)); } </script> <p id="p1" draggable="true" ondragstart="dragstart_handler(event)">this element is draggable.</p> <div id="target" ondrop="drop_handler(event)" ondragover="dragover_handler(event)">drop zone</div> for more information, see: performing a drop drag end at the end of a drag operation, the dragend event fires at the source element — the element that was the target of th...

Node.insertBefore() - Web APIs
example example 1 <div id="parentelement"> <span id="childelement">foo bar</span> </div> <script> // create the new node to insert let newnode = document.createelement("span") // get a reference to the parent node let parentdiv = document.getelementbyid("childelement").parentnode // begin test case [ 1 ] : existing childelement (all works correctly) let sp2 = document.getelementbyid("childelement") parentdiv.insertbefore(newnode, sp2) // end test case [ 1 ] // begin test case [ 2 ] : childelement is of type undefined let sp2 = undefined // non-existent node of id "childelement" parentdiv.insertbefore(newnode, sp2) // implicit dynamic cast to t...
...t sp2 = "undefined" // non-existent node of id "childelement" parentdiv.insertbefore(newnode, sp2) // generates "type error: invalid argument" // end test case [ 3 ] </script> example 2 <div id="parentelement"> <span id="childelement">foo bar</span> </div> <script> // create a new, plain <span> element let sp1 = document.createelement("span") // get the reference element let sp2 = document.getelementbyid("childelement") // get the parent element let parentdiv = sp2.parentnode // insert the new element into before sp2 parentdiv.insertbefore(sp1, sp2) </script> note: there is no insertafter() method.
... // get the parent element let parentelement = document.getelementbyid('parentelement') // get the parent's first child let thefirstchild = parentelement.firstchild // create a new element let newelement = document.createelement("div") // insert the new element before the first child parentelement.insertbefore(newelement, thefirstchild) when the element does not have a first child, then firstchild is null.

Using the Payment Request API - Web APIs
const checkoutbutton = document.getelementbyid('checkout-button'); if (window.paymentrequest) { let request = new paymentrequest(buildsupportedpaymentmethodnames(), buildshoppingcartdetails()); checkoutbutton.addeventlistener('click', function() { request.show().then(function(paymentresponse) { // handle successful payment }).catch(function(error) { // handle cancelled or failed payment.
... const checkoutbutton = document.getelementbyid('checkout-button'); checkoutbutton.innertext = "loading..."; if (window.paymentrequest) { let request = new paymentrequest(buildsupportedpaymentmethodnames(), buildshoppingcartdetails()); request.canmakepayment().then(function(canmakeafastpayment) { if (canmakeafastpayment) { checkoutbutton.innertext = "fast checkout with w3c"; } else { checkoutbutton.innertext = "se...
... const additionaldetailscontainer = document.getelementbyid('additional-details-container'); additionaldetailscontainer.style.display = 'block'; window.scrollto(additionaldetailscontainer.getboundingclientrect().x, 0); }).catch(function(error) { // handle error.

Window.pageYOffset - Web APIs
integer euismod lectus a ipsum pellentesque lacinia.</p> `; document.getelementbyid("frame").contentdocument .body.innerhtml = contenthtml; in this example, an <iframe> is created and filled with content, then a specific element within the document is scrolled into view in the frame.
... <iframe id="frame"> </iframe> <div id="info"> </div> javascript var frame = document.getelementbyid("frame"); var framedoc = frame.contentdocument; var info = document.getelementbyid("info"); var target = framedoc.getelementbyid("overview"); framedoc.scrollingelement.scrolltop = target.offsettop; info.innertext = "y offset after scrolling: " + frame.contentwindow.pageyoffset + " pixels"; the javascript code begins by getting into frame and info the <iframe> element that cont...
...it then gets a reference to the element we want to scroll into view calling getelementbyid() on the frame's htmliframeelement.contentdocument.

ARIA: button role - Accessibility
color: white; cursor: default; } [role="button"]:hover, [role="button"]:focus, [role="button"]:active { background-color: white; color: navy; } ul { list-style: none; } javascript function handlecommand(event) { // handles both mouse clicks and keyboard // activate with enter or space // get the new name value from the input element let newnameinput = document.getelementbyid('newname'); let name = newnameinput.value; newnameinput.value = ''; // clear the text field newnameinput.focus(); // give the text field focus to enable entering and additional name.
... let list = document.getelementbyid('namelist'); list.appendchild(listitem); } } toggle button example in this snippet a <span> element is converted to a toggle button using the button role and the aria-pressed attribute.
...et); } function handlebtnkeydown(event) { // check to see if space or enter were pressed if (event.key === " " || event.key === "enter" || event.key === "spacebar") { // "spacebar" for ie11 support // prevent the default action to stop scrolling when space is pressed event.preventdefault(); togglebutton(event.target); } } function togglebutton(element) { var audio = document.getelementbyid('audio'); // check to see if the button is pressed var pressed = (element.getattribute("aria-pressed") === "true"); // change aria-pressed to the opposite state element.setattribute("aria-pressed", !pressed); // toggle the play state of the audio file if(pressed) { audio.pause(); } else { audio.play(); } } result accessibility concerns buttons are interactive contro...

Web applications and ARIA FAQ - Accessibility
var progressbar = document.getelementbyid("percent-loaded"); // set its aria roles and states, so that assistive technologies know what kind of widget it is.
...and here is the javascript code that will ensure the progress bar still works in older browsers: var progressbar = document.getelementbyid("progress-bar"); // check to see if the browser supports the html5 <progress> tag.
... document.getelementbyid("update-button").addeventlistener("click", function (e) { updateprogress(75); e.preventdefault(); }, false); } initdemo(); how do assistive technologies work?

Getting Started - Developer guides
<button id="ajaxbutton" type="button">make a request</button> <script> (function() { var httprequest; document.getelementbyid("ajaxbutton").addeventlistener('click', makerequest); function makerequest() { httprequest = new xmlhttprequest(); if (!httprequest) { alert('giving up :( cannot create an xmlhttp instance'); return false; } httprequest.onreadystatechange = alertcontents; httprequest.open('get', 'test.html'); httprequest.send(); } function alertcontents() { if (htt...
...to our html so the user can enter their name: <label>your name: <input type="text" id="ajaxtextbox" /> </label> <span id="ajaxbutton" style="cursor: pointer; text-decoration: underline"> make a request </span> we'll also add a line to our event handler to get the user's data from the text box and send it to the makerequest() function along with the url of our server-side script: document.getelementbyid("ajaxbutton").onclick = function() { var username = document.getelementbyid("ajaxtextbox").value; makerequest('test.php',username); }; we need to modify makerequest() to accept the user data and pass it along to the server.
... <!doctype html> <html> <head> <meta charset="utf-8"> <title>xhr log time</title> <style> </style> </head> <body> <p id="writedata" class="data">off-line</p> <p id="laststamp">no data yet</p> <script> const fulldata = document.getelementbyid('writedata'); const lastdata = document.getelementbyid('laststamp'); function fetchdata() { console.log('fetching updated data.'); let xhr = new xmlhttprequest(); xhr.open("get", "time-log.txt", true); xhr.onload = function() { updatedisplay(xhr.response); } xhr.send(); } function updatedisplay(text) { fulldata.textcontent = text...

Communicating With Other Scripts - Archive of obsolete content
includes a button and a page script: <html> <head> <meta charset="utf-8"> </head> <body> <input id="message" type="button" value="send a message"/> <script type="text/javascript" src="page-script.js"></script> </body> </html> the content script "content-script.js" adds an event listener to the button, that sends a custom event containing a message: var messenger = document.getelementbyid("message"); messenger.addeventlistener("click", sendcustomevent, false); function sendcustomevent() { var greeting = {"greeting" : "hello world"}; var event = document.createevent('customevent'); event.initcustomevent("addon-message", true, true, greeting); document.documentelement.dispatchevent(event); } finally, the page script "page-script.js" listens for the message and logs the gre...
...from firefox 30 this sharing requires an extra step: the content script needs to explicitly clone the message payload into the page script's scope using the global cloneinto() function: var messenger = document.getelementbyid("message"); messenger.addeventlistener("click", sendcustomevent, false); function sendcustomevent() { var greeting = {"greeting" : "hello world"}; var cloned = cloneinto(greeting, document.defaultview); var event = document.createevent('customevent'); event.initcustomevent("addon-message", true, true, cloned); document.documentelement.dispatchevent(event); } messaging from page script...

Cross-domain Content Scripts - Archive of obsolete content
frame whose content is served from "http://en.m.wikipedia.org/": <!doctype html> <!-- page.html --> <html> <head></head> <body> <iframe id="wikipedia" src="http://en.m.wikipedia.org/"></iframe> </body> </html> the "page-script.js" file locates "today's featured article" and sends its content to "main.js": // page-script.js var iframe = window.document.getelementbyid("wikipedia"); var todaysfeaturedarticle = iframe.contentwindow.document.getelementbyid("mp-tfa"); self.postmessage(todaysfeaturedarticle.textcontent); for this to work, we need to add the "cross-domain-content" key to "package.json": "permissions": { "cross-domain-content": ["http://en.m.wikipedia.org/"] } the add-on should successfully retrieve the iframe's content.
.../ panel-script.js var url = "http://datapoint.metoffice.gov.uk/public/data/txt/wxfcs/regionalforecast/json/500?key=your-api-key"; self.port.on("show", function () { var request = new xmlhttprequest(); request.open("get", url, true); request.onload = function () { var jsonresponse = json.parse(request.responsetext); var summary = getsummary(jsonresponse); var element = document.getelementbyid("forecast_summary"); element.textcontent = summary; }; request.send(); }); function getsummary(forecast) { return forecast.regionalfcst.fcstperiods.period[0].paragraph[0].$; } finally, we need to add the "cross-domain-content" key to "package.json": "permissions": { "cross-domain-content": ["http://datapoint.metoffice.gov.uk"] } content permissions and unsafewindow if you use "...

panel - Archive of obsolete content
var textarea = document.getelementbyid("edit-box"); textarea.addeventlistener('keyup', function onkeyup(event) { if (event.keycode == 13) { // remove the newline.
...var textarea = document.getelementbyid("edit-box"); textarea.addeventlistener('keyup', function onkeyup(event) { if (event.keycode == 13) { // remove the newline.

widget - Archive of obsolete content
next, we write a content script that listens for click events on each icon and sends the corresponding message to the main add-on code: var play_button = document.getelementbyid("play-button"); play_button.onclick = function() { self.port.emit("play"); } var pause_button = document.getelementbyid("pause-button"); pause_button.onclick = function() { self.port.emit("pause"); } var stop_button = document.getelementbyid("stop-button"); stop_button.onclick = function() { self.port.emit("stop"); } we save this file in the add-on's data directory as "button-script.js".
... first, in the content script, change self to addon, and wrap it in a function: function init() { var play_button = document.getelementbyid("play-button"); play_button.onclick = function() { addon.port.emit("play"); } var pause_button = document.getelementbyid("pause-button"); pause_button.onclick = function() { addon.port.emit("pause"); } var stop_button = document.getelementbyid("stop-button"); stop_button.onclick = function() { addon.port.emit("stop"); } } next, add a script tag to reference "button-...

Bootstrapped extensions - Archive of obsolete content
you need to look up the relevant application ui elements by their id by calling document.getelementbyid(), then manipulate them to inject your ui.
... for example, you can get access to the menu bar in firefox with document.getelementbyid("main-menubar").

Dialogs and Prompts - Archive of obsolete content
r"><label value="name:"/><textbox id="name"/></row> <row align="center"><label value="description:"/><textbox id="description"/></row> <row align="center"><spacer/><checkbox id="enabled" label="check to enable"/></row> </rows> </grid> </dialog> mydialog.js: // called once when the dialog displays function onload() { // use the arguments passed to us by the caller document.getelementbyid("name").value = window.arguments[0].inn.name; document.getelementbyid("description").value = window.arguments[0].inn.description; document.getelementbyid("enabled").checked = window.arguments[0].inn.enabled; } // called once if and only if the user clicks ok function onok() { // return the changed arguments.
... // notice if user clicks cancel, window.arguments[0].out remains null // because this function is never called window.arguments[0].out = {name:document.getelementbyid("name").value, description:document.getelementbyid("description").value, enabled:document.getelementbyid("enabled").checked}; return true; } see also passing parameter to a dialog and getting return values from it.

HTML in XUL for rich tooltips - Archive of obsolete content
var htmltip = { onload: function() { //at any point you can save an html string to a xul attribute for later injection into the tooltip document.getelementbyid("htmltip1").setattribute("tooltiphtml", "<font color='red'>red foo</font>") document.getelementbyid("htmltip2").setattribute("tooltiphtml", "<font color='green'>green foo</font>") }, onmousetooltip: function(event) { //get the html tooltip string assigned to the element that the mouse is over (which will soon launch the tooltip) var txt = event.target.getattribute("tooltiphtml"); // get th...
...e html div element that is inside the custom xul tooltip var div = document.getelementbyid("myhtmltipdiv"); //clear the html div element of any prior shown custom html while(div.firstchild) div.removechild(div.firstchild); //safely convert html string to a simple dom object, stripping it of javascript and more complex tags var injecthtml = components.classes["@mozilla.org/feed-unescapehtml;1"] .getservice(components.interfaces.nsiscriptableunescapehtml) .parsefragment(txt, false, null, div); //attach the dom object to the html div element div.appendchild(injecthtml); } } window.addeventlistener('load', htmltip.onload, false); in the xul overlay, xmlns:html is used to enable html tags to be used inside the xul.

Miscellaneous - Archive of obsolete content
</div> <script type="text/javascript"> var elm = document.getelementbyid("scrollarea"); elm.addeventlistener("dommousescroll", function scroll(event){ //event.detail is positive for a downward scroll, negative for an upward scroll alert("scrolling " + event.detail + " lines"); }, false); </script> if you do not receive a dommousescroll event while holding any of the modifier keys (ctrl,shift,alt,meta) you should check the mousewheel.withcontrolkey.action...
...pet.length; var currentvalue = element.value; var beforetext = currentvalue.substring(0, element.selectionstart); var aftertext = currentvalue.substring(element.selectionend, currentvalue.length); element.value = beforetext + snippet + aftertext; element.focus(); //put the cursor after the inserted text element.setselectionrange(selectionend, selectionend); } inserttext(document.getelementbyid("example"), "the text to be inserted"); disabling javascript programmatically // disable js in the currently active tab from the context of browser.xul gbrowser.docshell.allowjavascript = false; if this isn't your browser, you should save the value and restore it when finished.

Tree - Archive of obsolete content
eview = tree.treeboxobject.view; for (var i = 0; i < treeview.rowcount; i++) { if (treeview.iscontainer(i) && treeview.iscontaineropen(i)) treeview.toggleopenstate(i); } getting the text from the selected row assuming the given <tree>: <tree id="my-tree" seltype="single" onselect="ontreeselected()"> use the following javascript: function ontreeselected(){ var tree = document.getelementbyid("my-tree"); var cellindex = 0; var celltext = tree.view.getcelltext(tree.currentindex, tree.columns.getcolumnat(cellindex)); alert(celltext); } getting the tree item from the focused row assuming <tree id="my-tree">, you can use the following to get the tree item: var view = document.getelementbyid("my-tree").view; var sel = view.selection.currentindex; //returns -1 if the tree is n...
...for example, assuming the given <tree>: <tree id="my-tree" onclick="ontreeclicked(event)"> use the following javascript: function ontreeclicked(event){ var tree = document.getelementbyid("my-tree"); var tbo = tree.treeboxobject; // get the row, col and child element at the point var row = { }, col = { }, child = { }; tbo.getcellat(event.clientx, event.clienty, row, col, child); var celltext = tree.view.getcelltext(row.value, col.value); alert(celltext); } getting the selected indices of a multiselect tree var start = {}, end = {}, numranges = tree.view.selectio...

Appendix E: DOM Building and Insertion (HTML & XUL) - Archive of obsolete content
type: "menu", label: "test button label", tooltiptext: "test button tooltip", removable: true, key: "mytestbutton123" }, [ "menupopup", { onpopupshowing: function(event) { addentrytopopup(this, document, window); } }, null ] ]; var capturednodes = {}; var toolbox = doc.getelementbyid("navigator-toolbox"); var palette = toolbox.palette; var domfragment = jsontodom(jsontemplatebtn, document, capturednodes); palette.appendchild(domfragment); alert("capturednodes contains any created nodes that have optionally been captured (for later convenient javascript access) by giving them a 'key' attribute; for example: " + capturednodes.mytestbutton123); another example this here is a...
... var href = "http://www.google.com/"; var text = "google"; document.getelementbyid("target-div").innerhtml = '<div>\ <a href="' + escapehtml(href) + '" target="_top">' + escapehtml(text) + '</a>\ </div>' it needs to be stressed that this method should not be used in new code and is only a temporary measure to shore up legacy code bases.

JavaScript Object Management - Archive of obsolete content
*/ init : function(aevent) { this._stringbundle = document.getelementbyid("xulschoolhello-string-bundle"); // you can make changes to the window dom here.
...if you really need to do something like this anyway, one way to do it is to have a timeout execute the code after a delay: init : function(aevent) { let that = this; this._stringbundle = document.getelementbyid("xs-hw-string-bundle"); window.settimeout( function() { window.alert(that._stringbundle.getstring("xulschoolhello.greeting.label")); }, 0); } the settimeout function executes the function in the first parameter, after a delay in miliseconds specified by the second parameter.

The Essentials of an Extension - Archive of obsolete content
sayhello : function(aevent) { let stringbundle = document.getelementbyid("xulschoolhello-string-bundle"); let message = stringbundle.getstring("xulschoolhello.greeting.label"); window.alert(message); } and, finally, this is our function declaration.
...you cannot dynamically change an attribute value with a new dtd key, you have to set the new value directly: let helloitem = document.getelementbyid("xulschoolhello-hello-menu-item"); // the alert will say "hello world!" alert(helloitem.getattribute("label")); // wrong helloitem.setattribute("label", "&xulschoolhello.hello2.label;"); // better helloitem.setattribute("label", "alternate message"); // right!

Creating a dynamic status bar extension - Archive of obsolete content
function inforeceived() { var samplepanel = document.getelementbyid('stockwatcher'); var output = httprequest.responsetext; if (output.length) { // remove whitespace from the end of the string; // this gets rid of the end-of-line characters output = output.replace(/\w*$/, ''); // build the tooltip string var fieldarray = output.split(','); // assert that fieldarray[0] == 'goog' samplepanel.label = 'goog: ' + fieldarray[1]; sa...
...mplepanel.tooltiptext = 'chg: ' + fieldarray[4] + ' | ' + 'open: ' + fieldarray[5] + ' | ' + 'low: ' + fieldarray[6] + ' | ' + 'high: ' + fieldarray[7] + ' | ' + 'vol: ' + fieldarray[8]; } } the first thing we do here is get the status bar panel into the variable samplepanel by calling the document.getelementbyid() dom function.

Localizing an extension - Archive of obsolete content
we add to refreshinformation() the following code: var stringsbundle = document.getelementbyid("string-bundle"); var changestring = stringsbundle.getstring('changestring') + " "; var openstring = stringsbundle.getstring('openstring') + " "; var lowstring = stringsbundle.getstring('lowstring') + " "; var highstring = stringsbundle.getstring('highstring') + " "; var volumestring = stringsbundle.getstring('volumestring') + " "; this code gets a reference to the string bundle element we ...
...added to stockwatcher2.xul by calling document.getelementbyid(), specifying the id "string-bundle".

Visualizing an audio spectrum - Archive of obsolete content
<!doctype html> <html> <head> <title>javascript spectrum example</title> </head> <body> <audio id="audio-element" src="song.ogg" controls="true" style="width: 512px;"> </audio> <div><canvas id="fft" width="512" height="200"></canvas></div> <script> var canvas = document.getelementbyid('fft'), ctx = canvas.getcontext('2d'), channels, rate, framebufferlength, fft; function loadedmetadata() { channels = audio.mozchannels; rate = audio.mozsamplerate; framebufferlength = audio.mozframebufferlength; fft = new fft(framebufferlength / channels, rate); } function...
...vas before drawing spectrum ctx.clearrect(0,0, canvas.width, canvas.height); for (var i = 0; i < fft.spectrum.length; i++ ) { // multiply spectrum by a zoom value magnitude = fft.spectrum[i] * 4000; // draw rectangle bars for each frequency bin ctx.fillrect(i * 4, canvas.height, 3, -magnitude); } } var audio = document.getelementbyid('audio-element'); audio.addeventlistener('mozaudioavailable', audioavailable, false); audio.addeventlistener('loadedmetadata', loadedmetadata, false); // fft from dsp.js, see below var fft = function(buffersize, samplerate) { this.buffersize = buffersize; this.samplerate = samplerate; this.spectrum = new float32array(buffersize/2); ...

Monitoring downloads - Archive of obsolete content
onload: function() { // initialization code this.initialized = true; this.strings = document.getelementbyid("downloadlogger-strings"); this.dlmgr = components.classes["@mozilla.org/download-manager;1"] .getservice(components.interfaces.nsidownloadmanager); this.dlmgr.addlistener(downloadlogger); // open the database, placing its file in the profile directory this.dbfile = components.classes["@mozilla.org/file/directory_service;1"] .getservic...
..."profd", components.interfaces.nsifile); this.dbfile.append("downloadlogger.sqlite"); // get access to the storage service and open the database this.storageservice = components.classes["@mozilla.org/storage/service;1"] .getservice(components.interfaces.mozistorageservice); var dbconn = this.storageservice.opendatabase(this.dbfile); var loglist = document.getelementbyid("loglist"); var statement = dbconn.createstatement("select * from items"); // get all items in table try { while (statement.executestep()) { var row = document.createelement('listitem'); // add the cells to the row var cell = document.createelement('listcell'); var sourcestr = statement.getstring(0); row.setattribute("tooltiptext", sourcestr); ...

PyDOM - Archive of obsolete content
for example, let's say you have xul similar to pyxultest: top-level script code says something like: button = document.getelementbyid("some-button") button.foo = 0 and the button itself might look like: <button id="some-button" label="click here" onclick="event.target.foo += 1; print 'foo is now', event.target.foo"/> note that (a) we have stuck an arbitrary attribute on a dom element and (b) in all cases (e.g., event handler and top-level script), the dom node needs to be explicitly specified - the globals are the wi...
...the event handler could also have used getelementbyid - the point is that both the event handler and top-level script share the same namespace.

id - Archive of obsolete content
you can use this as a parameter to getelementbyid() and other dom functions and to reference the element in style sheets.
... example <button id="foo" label="click me" oncommand="dosomething()"/> <script> function dosomething(){ var mybutton = document.getelementbyid('foo'); mybutton.setattribute('label','the button was pressed'); } </script> a more abstract version of the above would be a <button id="foo" label="click me" oncommand="setwidgetlabel(this, 'i was pressed')"/> <script> function setwidgetlabel(idname, newcaption){ document.getelementbyid( idname.id ).setattribute('label',newcaption) } </script> not specifying the id attribute for a window or a prefwindow fills the console with the following warning message: warning: empty string passed to getelementbyid() see also name ...

label - Archive of obsolete content
see also treeitem.label, <label> element examples in javascript <label value="whaw" id="the-big-label" command="the-big-button"/> <button id="the-big-button" label="click me" oncommand="alert(document.getelementbyid('the-big-label').value)"/> <label id="mylabel" value="my label"/> <button label="click me" oncommand="document.getelementbyid('mylabel').setattribute('value','value changed');" /> <checkbox label="my checkbox" id="mycheckbox"/> <button label="another click" oncommand="document.getelementbyid('mycheckbox').setattribute('label','still not checked');"/> <button label="show label of checkbox" on...
...command="alert( document.getelementbyid('mycheckbox').getattribute('label') )"/> ...

Building accessible custom components in XUL - Archive of obsolete content
<code> var gfocuscell = null; function install_handlers() { var spreadsheet = window.document.getelementbyid('accjaxspreadsheet'); spreadsheet.addeventlistener('focus', spreadsheet_focus, true); spreadsheet.addeventlistener('click', spreadsheet_click, true); } function spreadsheet_focus(e) { if (e.target.tagname == 'grid') { if (!gfocuscell) { gfocuscell = e.target.getelementsbytagname('label')[0]; } gfocuscell.focus(); } else { gfocuscell = e...
...<code> function install_handlers() { var spreadsheet = window.document.getelementbyid('accjaxspreadsheet'); spreadsheet.addeventlistener('keypress', spreadsheet_keypress, true); spreadsheet.addeventlistener('focus', spreadsheet_focus, true); spreadsheet.addeventlistener('click', spreadsheet_click, true); } </code> with this new event handler and associated helper functions, we can navigate between cells and headers using the arrow keys.

Extensions - Archive of obsolete content
function init() { var contextmenu = document.getelementbyid("contentareacontextmenu"); if (contextmenu) contextmenu.addeventlistener("popupshowing", thumbnailsshowhideitems, false); } function thumbnailsshowhideitems(event) { var show = document.getelementbyid("thumbnail-show"); show.hidden = (document.popupnode.localname != "img"); } the init function should be called within the handler for the load event so that the popupshowing event handl...
... function thumbnailsshowhideitems(event) { var show = document.getelementbyid("thumbnail-show"); show.hidden = !(gcontextmenu.onimage || gcontextmenu.onlink); } ...

OpenClose - Archive of obsolete content
here is a complete example which uses a button to open a menu: <button label="open menu" oncommand="document.getelementbyid('editmenu').open = true;"/> <menu id="editmenu" label="edit"> <menupopup> <menuitem label="cut"/> <menuitem label="copy"/> <menuitem label="paste"/> </menupopup> </menu> this technique may be used for both menupopups that use the menu tag, the button tag and the toolbarbutton tag.
...here is an example mouse click event listener: function mouseclicked(event) { var panel = document.getelementbyid("some-panel"); panel.openpopup(null, "", event.clientx, event.clienty, false, false); } the openpopupatscreen method a second method, openpopupatscreen, may be used to open up a popup and place it at a specific screen coordinate.

Panels - Archive of obsolete content
for instance, using the search panel example above, we could add a button which closes the panel when pressed: <script> function dosearch() { document.getelementbyid("search-panel").hidepopup(); } </script> <toolbarbutton label="search" type="panel"> <panel id="search-panel" position="after_start"> <textbox id="search"/> <button label="search" oncommand="dosearch();"/> </panel> </toolbarbutton> in this example, the dosearch() function is called when the "search" button is pressed.
...for instance, to have the textbox initially focused in the example above: <panel id="search-panel" onpopupshown="document.getelementbyid('search').focus()"> to disable the adjusting of focus when a panel is opened, set the noautofocus attribute to true: <panel noautofocus="true"> this will cause the focus to remain on the element within the main window that has focus when the panel is opened.

PopupEvents - Archive of obsolete content
<script> function openfilemenu() { var filemenu = document.getelementbyid("file-menu"); filemenu.addeventlistener("popupshown", filemenuopened, false); filemenu.open = true; } function filemenuopened(event) { if (event.target != document.getelementbyid("file-menupopup")) return; var filemenu = document.getelementbyid("file-menu"); filemenu.removeeventlistener("popupshown", filemenuopened, false); var openmenu = document.getelementbyid("open-menu"); ...
...<panel onpopuphiding="document.getelementbyid('search').value = '';"> <textbox id="search"/> <button label="search" oncommand="dosearch();"/> </panel> you can prevent a popup from hiding by calling the event's preventdefault method.

Filtering - Archive of obsolete content
function applyfilter(country) { var cond = document.getelementbyid("cond"); var triple = document.getelementbyid("filtertriple"); if (country) { if (!triple) { triple = document.createelement("triple"); triple.id = "filtertriple"; triple.setattribute("subject", "?photo"); triple.setattribute("predicate", "http://www.xulplanet.com/rdf/country"); } triple.setattribute("object", country); cond.appendchild(triple); } e...
...lse if (triple) { cond.removechild(triple); } document.getelementbyid("photoslist").builder.rebuild(); } the 'country' argument to the applyfilter function holds the value to filter by.

SQLite Templates - Archive of obsolete content
you would likely want to add an id to the param element so that the getelementbyid method may be used to refer to it.
...we could later change the age to use in the query with a short script: function adjustage(min, max) { document.getelementbyid("minage").textcontent = min; document.getelementbyid("maxage").textcontent = max; document.getelementbyid("friends").builder.rebuild(); } this function takes two arguments, the minimum and maximum values to use.

Template Builder Interface - Archive of obsolete content
getservice(components.interfaces.nsirdfservice); var ds = rdf.getdatasource("http://www.xulplanet.com/ndeakin/tests/xul/template-guide-streets.rdf"); var tree = document.getelementbyid("thetree"); tree.database.adddatasource(ds); tree.builder.rebuild(); this is the typical way to add a datasource to an element, in this case to the tree with the id 'thetree'.
...for instance: var tree = document.getelementbyid("thetree"); tree.datasources = "template-guide-photos5.rdf template-guide-streets.rdf"; this will also change the datasources used.

Creating toolbar buttons (Customize Toolbar Window) - Archive of obsolete content
a simple document.getelementbyid('browsertoolbarpalette') will not work.
... the advantage to adding the toolbar button to the palette rather than creating an element and then appendchild to the toolbar (document.getelementbyid('nav-bar')) or appendchild to the addon bar (document.getelementbyid('addon-bar')) is that once in the toolbar palette, users can configure it through the customize menu.

Adding Properties to XBL-defined Elements - Archive of obsolete content
that way, all you need is to get a reference to the element (using document.getelementbyid or a similar function) and then get or set the additional properties and call the methods on it.
...xul: <box id="random-box" class="randomizer"/> <button label="generate" oncommand="document.getelementbyid('random-box').number=math.random();"/> <button label="show" oncommand="alert(document.getelementbyid('random-box').number)"/> xbl: <binding id="randomizer"> <implementation> <field name="number"/> </implementation> </binding> a number field has been defined in the binding, which stores the random number.

Box Objects - Archive of obsolete content
example 2 : source view <script> function showpositionandsize() { var labelbox = document.getelementbyid('thelabel').boxobject; alert("position is (" + labelbox.x + "," + labelbox.y + ") and size is (" + labelbox.width + "," + labelbox.height + ")"); } </script> <button label="hide" oncommand="document.getelementbyid('thelabel').hidden = true;"/> <button label="show" oncommand="document.getelementbyid('thelabel').hidden = false;"/> <button label="collapse" ...
... oncommand="document.getelementbyid('thelabel').collapsed = true;"/> <button label="uncollapse" oncommand="document.getelementbyid('thelabel').collapsed = false;"/> <button label="show position/size" oncommand="showpositionandsize();"/> <label id="thelabel" value="i am a label"/> note that if you hide and collapse the label, it will be treated as hidden.

Creating Dialogs - Archive of obsolete content
var somefile=document.getelementbyid('enterfile').value; window.opendialog("chrome://findfile/content/showdetails.xul","showmore", "chrome",somefile); in this example the dialog showdetails.xul is displayed.
...for example: var fl = window.arguments[0]; document.getelementbyid('thefile').value = fl; this is an effective way to pass values to the new window.

Custom Tree Views - Archive of obsolete content
function setview(){ document.getelementbyid('my-tree').view = treeview; } the following presents the example together.
...ction(row){ return false; }, isseparator: function(row){ return false; }, issorted: function(){ return false; }, getlevel: function(row){ return 0; }, getimagesrc: function(row,col){ return null; }, getrowproperties: function(row,props){}, getcellproperties: function(row,col,props){}, getcolumnproperties: function(colid,col,props){} }; function setview(){ document.getelementbyid('my-tree').view = treeview; } </script> <tree id="my-tree" flex="1"> <treecols> <treecol id="namecol" label="name" flex="1"/> <treecol id="datecol" label="date" flex="1"/> </treecols> <treechildren/> </tree> </window> in the image, you can see two columns, each with data taken from the getcelltext() function.

More Event Handlers - Archive of obsolete content
example 2 : source view <hbox id="outerbox"> <button id="okbutton" label="ok"/> </hbox> <script> function buttonpressed(event){ alert('button was pressed!'); } function boxpressed(event){ alert('box was pressed!'); event.stoppropagation(); } var button = document.getelementbyid("okbutton"); button.addeventlistener('command',buttonpressed,true); var outerbox = document.getelementbyid("outerbox"); outerbox.addeventlistener('command',boxpressed,true); </script> here, an event listener has been added to the button and another event listener has been added to the box.
...here is an example which displays the current mouse coordinates: example 4 : source view <script> function updatemousecoordinates(e){ var text = "x:" + e.clientx + " y:" + e.clienty; document.getelementbyid("xy").value = text; } </script> <label id="xy"/> <hbox width="400" height="400" onmousemove="updatemousecoordinates(event);"/> in this example, the size of the box has been set explicitly so the effect is easier to see.

Property Files - Archive of obsolete content
var strbundle = document.getelementbyid("strings"); var nofilesfound=strbundle.getstring("notfoundalert"); alert(nofilesfound); this example first gets a reference to the bundle using its id then, it looks up the string 'notfoundalert' in the property file.
...var dir = "/usr/local/document"; var count = 10; var strbundle = document.getelementbyid("strings"); var result = strbundle.getformattedstring("resultmessage", [ dir, count ]); alert(result); this example will display following message in an alert box.

Tree View Details - Archive of obsolete content
function init() { document.getelementbyid("elementlist").view = treeview; } the custom tree view will need to implement a number of methods, of which the important ones will be examined individually.
... cycleheader: function(col, elem) {}, selectionchanged: function() {}, cyclecell: function(idx, column) {}, performaction: function(action) {}, performactiononcell: function(action, index, column) {}, getrowproperties: function(idx, prop) {}, getcellproperties: function(idx, column, prop) {}, getcolumnproperties: function(column, element, prop) {}, }; function init() { document.getelementbyid("elementlist").view = treeview; } ]]></script> </window> next, we'll look in more detail at the tree box object.

XUL Event Propagation - Archive of obsolete content
in another example, an onload event handler for a xul window can register a box element to capture all the click events that are raised from its child elements: var bbox = document.getelementbyid("bigbox"); if (bbox) bbox.addeventlistener("click", function() { alert('captured'); }, true); ...
...the syntax for this in xul is as follows: element = document.getelementbyid("id of the element"); element.addeventlistener(event name, event handler function, whether to register a capturing listener); the event handler code argument can be in-line code or a function.

tree - Archive of obsolete content
pe column: function getcellchecked(tree, columnid) { var arr = []; var column = tree.columns.getnamedcolumn(columnid); for (var i = 0; i < tree.view.rowcount; i++) { if (tree.view.getcellvalue(i, column) == 'true') arr.push(i); } return arr; } to get the text value for a specific column (for example column 'age') from the currently focused row in the tree: var t = document.getelementbyid('mytree'); document.title = t.view.getcelltext(t.currentindex,t.columns.getnamedcolumn('age')); to select the checkbox and display the cell's text value, you can use code like the following.
...oz-tree-cell-text(selected) { color: #000000; } treechildren::-moz-tree-cell-text(odd, selected) { color: #000000; } treechildren::-moz-tree-row(hover) {background-color: #ffffaa !important;} treechildren:-moz-tree-column { border-right:1px solid rgb(220,220,220) !important; } the javascript to get the text for the selected row/rows: function getrowcellvalues() { var tree = document.getelementbyid('mytree'); for (var i = 0; i < tree.view.rowcount; i++) { if (tree.view.getcellvalue(i, tree.columns.getcolumnat(0)) == 'true'){ alert(tree.view.getcelltext(i, tree.columns.getnamedcolumn("name"))); } } } this way, you can get the tree cell values of the selected checkbox of the corresponding row.

How to enable locale switching in a XULRunner application - Archive of obsolete content
nsitoolkitchromeregistry); var selectedlocale = xulchromereg.getselectedlocale("localeswitchdemo"); var availablelocales = toolkitchromereg.getlocalesforpackage("localeswitchdemo"); // render locale menulist by iterating through the query result from getlocalesforpackage() const xul_ns = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"; var localelistbox = document.getelementbyid("locale-listbox"); var selecteditem = null; while(availablelocales.hasmore()) { var locale = availablelocales.getnext(); var listitem = document.createelementns(xul_ns, "listitem"); listitem.setattribute("value", locale); listitem.setattribute("label", locale); if (locale == selectedlocale) { // is this the current locale?
... var localelistbox = document.getelementbyid("locale-listbox"); var newlocale = localelistbox.selecteditem.value; // write preferred locale to local user config var prefs = components.classes["@mozilla.org/preferences-service;1"].

Back to the Server: Server-Side JavaScript On The Rise - Archive of obsolete content
listing 7 - manipulating the dom server-side <script runat="server"> window.onserverload = function() { document.getelementbyid( "out-logger" ).innerhtml = jaxer.file.read( "dump.txt" ); } </script> the code in listing 7 is executed server-side and takes advantage of the onserverload event which ensures that we have a complete dom before trying to access it.
...a <script> function formhandler() { // get the form values var name = txt_name.getvalue(); var email = txt_email.getvalue(); var message = txt_message.getvalue(); // if the form passes validation client-side, submit results to the processor if( validatecomments( name, email, message ) ) { formprocessor( name, email, message ); // update the logger with the most recent entry document.getelementbyid( "out-logger" ).innerhtml += "name: " + name + "<br/>email: " + email + "<br/>message: " + message + "<br/><br/>"; } else { ext.msg.alert( "error", "please enter the required fields" ); } } </script> <!-- processes the form contents --> <script runat="server"> function formprocessor( name, email, message ) { // perform the same validation of the data server-side if( !validatecomments( name...

Displaying a graphic with audio samples - Archive of obsolete content
e html> <html> <head> <title>javascript spectrum example</title> </head> <body> <audio id="audio-element" src="revolve.ogg" controls="true" style="width: 512px;"> </audio> <div><canvas id="fft" width="512" height="200"></canvas></div> <img id="mozlogo" style="display:none" src="mozilla2.png"></img> <script> var canvas = document.getelementbyid('fft'), ctx = canvas.getcontext('2d'), channels, rate, framebufferlength, fft; function loadedmetadata() { channels = audio.mozchannels; rate = audio.mozsamplerate; framebufferlength = audio.mozframebufferlength; fft = new fft(framebufferlength / channels, rate); } ...
...tx.fillrect (0,0, canvas.width, canvas.height); ctx.fillstyle = "rgb(255,255,255)"; for (var i = 0; i < signal.length; i++ ) { // multiply spectrum by a zoom value magnitude = signal[i] * 1000; // draw rectangle bars for each frequency bin ctx.fillrect(i * 4, canvas.height, 3, -magnitude); } ctx.drawimage(document.getelementbyid('mozlogo'),0,0, canvas.width, canvas.height); } var audio = document.getelementbyid('audio-element'); audio.addeventlistener('mozaudioavailable', audioavailable, false); audio.addeventlistener('loadedmetadata', loadedmetadata, false); </script> </body> </html> ...

GLSL Shaders - Game development
applying the shaders to actually apply the newly created shaders to the cube, comment out the basicmaterial definition first: // var basicmaterial = new three.meshbasicmaterial({color: 0x0095dd}); then, create the shadermaterial: var shadermaterial = new three.shadermaterial( { vertexshader: document.getelementbyid( 'vertexshader' ).textcontent, fragmentshader: document.getelementbyid( 'fragmentshader' ).textcontent }); this shader material takes the code from the scripts and applies it to the object the material is assigned to.
...h, height); renderer.setclearcolor(0xdddddd, 1); document.body.appendchild(renderer.domelement); var scene = new three.scene(); var camera = new three.perspectivecamera(70, width/height); camera.position.z = 50; scene.add(camera); var boxgeometry = new three.boxgeometry(10, 10, 10); var shadermaterial = new three.shadermaterial( { vertexshader: document.getelementbyid( 'vertexshader' ).textcontent, fragmentshader: document.getelementbyid( 'fragmentshader' ).textcontent }); var cube = new three.mesh(boxgeometry, shadermaterial); scene.add(cube); cube.rotation.set(0.4, 0.2, 0); function render() { requestanimationframe(render); renderer.render(scene, camera); } render(); css body { margin: 0; padding: 0; fo...

Images in HTML - Learn web development
th: 95%"> <img> </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...
...x; width: 95%"> </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var solution = document.getelementbyid('solution'); var output = document.queryselector('.output'); var code = textarea.value; var userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = ht...

Looping code - Learn web development
d(para); </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...
...ontent += ; </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...

Making decisions in your code — conditionals - Learn web development
: 0; } .output li { display: block; float: left; width: 25%; border: 2px solid white; padding: 5px; height: 40px; background-color: #4a2db6; color: white; } html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...
... textcolor; }</textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...

Manipulating documents - Learn web development
there are older methods available for grabbing element references, such as: document.getelementbyid(), which selects an element with a given id attribute value, e.g.
...const elementref = document.getelementbyid('myid').

Arrays - Learn web development
er 4 // number 5 let itemtext = 0; const listitem = document.createelement('li'); listitem.textcontent = itemtext; list.appendchild(listitem); } totalbox.textcontent = 'total: $' + total.tofixed(2); </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...
...ocus(); } } </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); let code = textarea.value; let userentry = textarea.value; function updatecode() { eval(textarea.value); } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentry = jssolution; solution.value = 'show solution'; updatecod...

Basics
> <msup> <mi>y</mi> <mn>4</mn> </msup> </mrow> <mo>+</mo> <msup> <mi>y</mi> <mn>5</mn> </msup> </mrow> </maction> </mtd> </mtr> </mtable> </mtd> </mtr> </mtable> </math> </div> css content .control { text-decoration: none; font-weight: bold; font-size: 200%; } input { color: red; } [class="inputmath"] { border: 1px dotted; } javascript content function setselection(id,value) { document.getelementbyid(id).setattribute("selection",value); } function expand() { setselection("a11","2"); setselection("a12","2"); setselection("a13","2"); setselection("a21","2"); setselection("a22","2"); setselection("a23","2"); setselection("a31","2"); setselection("a32","2"); setselection("a33","2"); setselection("a41","2"); setselection("a42","2"); setselection("a43","2"); } function unexpand() { ...
... setselection("a11","1"); setselection("a12","1"); setselection("a13","1"); setselection("a21","1"); setselection("a22","1"); setselection("a23","1"); setselection("a31","1"); setselection("a32","1"); setselection("a33","1"); setselection("a41","1"); setselection("a42","1"); setselection("a43","1"); } function incrementinput(inputid, increment) { var inputelement = document.getelementbyid(inputid); var size = parseint(inputelement.size) + increment; if (size <= 0) size = 1 inputelement.size = size; } and there could be more...

MathML Demo: <mspace> - space
f="javascript:downdepth();" title="decrease depth">-</a> <math display="block"> <mstyle displaystyle="true"> <msqrt> <mrow> <mn>3</mn> <mspace style="background-color: yellow" id="thespace" height="0.1ex" depth="0.1ex" width="0.1em" /> <mi>x</mi> </mrow> </msqrt> </mstyle> </math> </p> javascript content var height=0; var width=0; var depth=0; function upheight() { height++; document.getelementbyid("thespace").setattribute("height",height+".1ex"); } function downheight() { height--; document.getelementbyid("thespace").setattribute("height",height+".1ex"); } function upwidth() { width++; document.getelementbyid("thespace").setattribute("width",width+".1em"); } function downwidth() { width--; document.getelementbyid("thespace").setattribute("width",width+".1em"); } function updept...
...h() { depth++; document.getelementbyid("thespace").setattribute("depth",depth+".1ex"); } function downdepth() { depth--; document.getelementbyid("thespace").setattribute("depth",depth+".1ex"); } ...

Scroll-linked effects
<body style="height: 5000px" onscroll="document.getelementbyid('toolbar').style.top = math.max(100, window.scrolly) + 'px'"> <div id="toolbar" style="position: absolute; top: 100px; width: 100px; height: 20px; background-color: green"></div> </body> this implementation of sticky positioning relies on the scroll event listener to reposition the "toolbar" div.
... } else if (math.abs(destination - window.scrolly) < 200) { scrollto(window.scrollx, window.scrolly + ((destination - window.scrolly) / 2)); settimeout(snap, 20, destination); } } var timeoutid = null; addeventlistener("scroll", function() { if (timeoutid) cleartimeout(timeoutid); timeoutid = settimeout(snap, 200, parseint(document.getelementbyid('snaptarget').style.top)); }, true); </script> <div id="snaptarget" class="snaptarget" style="position: relative; top: 200px; width: 100%; height: 200px; background-color: green"></div> </body> in this example, there is a scroll event listener which detects if the scroll position is within 200 pixels of the top of the "snaptarget" div.

Components.utils.cloneInto
e same mechanism as that used in components.utils.exportfunction: // add-on script var addonscriptobject = { greetme: function() { alert("hello from add-on"); } }; contentwindow.addonscriptobject = cloneinto(addonscriptobject, contentwindow, {clonefunctions: true}); // page script var test = document.getelementbyid("test"); test.addeventlistener("click", function() { window.addonscriptobject.greetme(); }, false); cloning objects that contain dom elements by default, if the object you clone contains objects that are reflected from c++, such as dom elements, the cloning operation will fail with an error.
...{wrapreflectors:true} flag, then the object you clone is allowed to contain these objects: // add-on script var addonscriptobject = { body: contentwindow.document.body }; contentwindow.addonscriptobject = cloneinto(addonscriptobject, contentwindow, {wrapreflectors: true}); // page script var test = document.getelementbyid("test"); test.addeventlistener("click", function() { console.log(window.addonscriptobject.body.innerhtml); }, false); access to these objects in the target scope is subject to the normal security checks.

nsIMacDockSupport
ribute('label', 'show most recent window'); macmenuitem.setattribute('id', 'mymacmenuitem'); macmenuitem.addeventlistener('command', function(){ var docksupport = cc['@mozilla.org/widget/macdocksupport;1'].getservice(ci.nsimacdocksupport); docksupport.activateapplication(true); services.wm.getmostrecentwindow(null).focus() }) macmenu.appendchild(macmenuitem); var mainpopupset = win.document.getelementbyid('mainpopupset'); mainpopupset.appendchild(macmenu); let dockmenuelement = macmenu; //document.getelementbyid("menu_mac_dockmenu");66 let nativemenu = cc["@mozilla.org/widget/standalonenativemenu;1"].createinstance(ci.nsistandalonenativemenu); console.log('dockmenuelement:', dockmenuelement); nativemenu.init(dockmenuelement); docksupport.dockmenu = nativemenu; this replaces the default menu wit...
...m'); macmenuitem.setattribute('label', 'show most recent window'); macmenuitem.setattribute('id', 'mymacmenuitem'); macmenuitem.addeventlistener('command', function(){ var docksupport = cc['@mozilla.org/widget/macdocksupport;1'].getservice(ci.nsimacdocksupport); docksupport.activateapplication(true); services.wm.getmostrecentwindow(null).focus() }) services.appshell.hiddendomwindow.document.getelementbyid('menu_mac_dockmenu').appendchild(macmenuitem) this adds the "show most recent window" menuitem from the previous example as a third item.

Add to iPhoto
if (document.getelementbyid("contentareacontextmenu")) { document.getelementbyid("contentareacontextmenu").addeventlistener("popupshowing", iphoto.onpopup, false); } responding when the context menu is clicked when the user right-clicks an image, our handler gets called: onpopup: function() { var node = iphoto.getcurrentnode(); var item = document.getelementbyid("add-to-iphoto_menuitem"); if (item) { item.
...l, null, null, null); var appstr = "file:///applications/iphoto.app"; var appstrcf = corefoundation.cfstringcreatewithcharacters(null, appstr, appstr.length); var appurl = corefoundation.cfurlcreatewithstring(null, appstrcf, null); corefoundation.cfrelease(appstrcf); var b = corefoundation.cfurlgetfsref(appurl, ref.address()); if (!b) { var stringsbundle = document.getelementbyid("string-bundle"); alert(stringsbundle.getstring('alert_download_error_string')); } else { var array = ctypes.cast(mutablearray, corefoundation.cfarrayref); appservices.lsopenurlswithrole(array, 0, null, appparams.address(), null, 0); } corefoundation.cfrelease(appurl); // clean up corefoundation.cfrelease(array); } appservices.shutdown(); carbon.shu...

Flash Activation: Browser Comparison - Plugins
this can be done by calling a javascript function when the plugin is activated: function plugincreated() { // we don't need to see the plugin, so hide it by resizing var plugin = document.getelementbyid('myplugin'); plugin.height = 0; plugin.width = 0; plugin.callpluginmethod(); } the html, by default, specifies the flash object to be a size that makes it visible, like this: <!-- give the plugin an initial size so it is visible --> <object type="application/x-shockwave-flash" data="myapp.swf" id="myplugin" width="300" height="300"> <param name="callback" value="plugincreated()"> ...
...r html with a callback that calls the javascript function plugincreated(), like this: <object type="application/x-my-plugin" data="somedata.mytype" id="myplugin"> <param name="callback" value="plugincreated()"> </object> the plugincreated() function is then responsible for the setup of your script and any calls back into the plugin that you need to make: function plugincreated() { document.getelementbyid('myplugin').callpluginmethod(); } ...

Background Tasks API - Web APIs
let totaltaskcountelem = document.getelementbyid("totaltaskcount"); let currenttasknumberelem = document.getelementbyid("currenttasknumber"); let progressbarelem = document.getelementbyid("progress"); let startbuttonelem = document.getelementbyid("startbutton"); let logelem = document.getelementbyid("log"); next we have variables which reference the dom elements we need to interact with.
...- min + 1)) + min; } function decodetechnostuff() { totaltaskcount = 0; currenttasknumber = 0; updatedisplay(); let n = getrandomintinclusive(100, 200); for (i=0; i<n; i++) { let taskdata = { count: getrandomintinclusive(75, 150), text: "this text is from task number " + (i+1).tostring() + " of " + n }; enqueuetask(logtaskhandler, taskdata); } } document.getelementbyid("startbutton").addeventlistener("click", decodetechnostuff, false); decodetechnostuff() starts by zeroing the values of totaltaskcount (the number of tasks added to the queue so far) and currenttasknumber (the task currently being run), and then calls updatedisplay() to reset the display to its "nothing's happened yet" state.

CanvasPattern.setTransform() - Web APIs
html <canvas id="canvas"></canvas> <svg id="svg1"></svg> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var svg1 = document.getelementbyid('svg1'); var matrix = svg1.createsvgmatrix(); var img = new image(); img.src = 'https://mdn.mozillademos.org/files/222/canvas_createpattern.png'; img.onload = function() { var pattern = ctx.createpattern(img, 'repeat'); pattern.settransform(matrix.rotate(-45).scale(1.5)); ctx.fillstyle = pattern; ctx.fillr...
... </div> <textarea id="code" class="playable-code" style="height:120px"> var img = new image(); img.src = 'https://mdn.mozillademos.org/files/222/canvas_createpattern.png'; img.onload = function() { var pattern = ctx.createpattern(img, 'repeat'); pattern.settransform(matrix.rotate(-45).scale(1.5)); ctx.fillstyle = pattern; ctx.fillrect(0, 0, 400, 400); };</textarea> var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var textarea = document.getelementbyid('code'); var reset = document.getelementbyid('reset'); var edit = document.getelementbyid('edit'); var code = textarea.value; var svg1 = document.getelementbyid('svg1'); var matrix = svg1.createsvgmatrix(); function drawcanvas() { ctx.clearrect(0, 0, canvas.width, canvas.height); eval(textarea.value); } re...

CanvasRenderingContext2D.addHitRegion() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); canvas.addeventlistener('mousemove', function(event) { if(event.region) { alert('ouch, my eye :('); } }); ctx.beginpath(); ctx.arc(100, 100, 75, 0, 2 * math.pi); ctx.linewidth = 5; ctx.stroke(); // eyes ctx.beginpath(); ctx.arc(70, 80, 10, 0, 2 * math.pi); ctx.arc(130, 80, 10, 0, 2 * math.pi); ctx.fill(); ctx.addhitregion({id: "eyes"}); ...
...ode" style="height:250px"> ctx.beginpath(); ctx.arc(100, 100, 75, 0, 2 * math.pi, false); ctx.linewidth = 5; ctx.stroke(); // eyes ctx.beginpath(); ctx.arc(70, 80, 10, 0, 2 * math.pi, false); ctx.arc(130, 80, 10, 0, 2 * math.pi, false); ctx.fill(); ctx.addhitregion({id: "eyes"}); // mouth ctx.beginpath(); ctx.arc(100, 110, 50, 0, math.pi, false); ctx.stroke();</textarea> var canvas = document.getelementbyid("canvas"); var ctx = canvas.getcontext("2d"); var textarea = document.getelementbyid("code"); var reset = document.getelementbyid("reset"); var edit = document.getelementbyid("edit"); var code = textarea.value; function drawcanvas() { ctx.clearrect(0, 0, canvas.width, canvas.height); eval(textarea.value); } reset.addeventlistener("click", function() { textarea.value = code; drawcanvas()...

CanvasRenderingContext2D.bezierCurveTo() - Web APIs
html <canvas id="canvas"></canvas> javascript // define canvas and context const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // define the points as {x, y} let start = { x: 50, y: 20 }; let cp1 = { x: 230, y: 30 }; let cp2 = { x: 150, y: 80 }; let end = { x: 250, y: 100 }; // cubic bézier curve ctx.beginpath(); ctx.moveto(start.x, start.y); ctx.beziercurveto(cp1.x, cp1.y, cp2.x, cp2.y, end.x, end.y); ctx.stroke(); // start and end points ctx.fillstyl...
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(30, 30); ctx.beziercurveto(120,160, 180,10, 220,140); ctx.stroke(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.beziercurveto' in that specification.

CanvasRenderingContext2D.clearRect() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.clearrect(0, 0, canvas.width, canvas.height); erasing part of a canvas this example draws a blue triangle on top of a yellowish background.
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // draw yellow background ctx.beginpath(); ctx.fillstyle = '#ff6'; ctx.fillrect(0, 0, canvas.width, canvas.height); // draw blue triangle ctx.beginpath(); ctx.fillstyle = 'blue'; ctx.moveto(20, 20); ctx.lineto(180, 20); ctx.lineto(130, 130); ctx.closepath(); ctx.fill(); // clear part of the canvas ctx.clearrect(10, 10, 120, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.cl...

CanvasRenderingContext2D.clip() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // create circular clipping region ctx.beginpath(); ctx.arc(100, 75, 50, 0, math.pi * 2); ctx.clip(); // draw stuff that gets clipped ctx.fillstyle = 'blue'; ctx.fillrect(0, 0, canvas.width, canvas.height); ctx.fillstyle = 'orange'; ctx.fillrect(0, 0, 100, 100); result specifying a path and a fillrule this example saves two rectangles to a p...
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // create clipping path let region = new path2d(); region.rect(80, 10, 20, 130); region.rect(40, 50, 100, 50); ctx.clip(region, "evenodd"); // draw stuff that gets clipped ctx.fillstyle = 'blue'; ctx.fillrect(0, 0, canvas.width, canvas.height); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.clip' in that specification.

CanvasRenderingContext2D.closePath() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(20, 140); // move pen to bottom-left corner ctx.lineto(120, 10); // line to top corner ctx.lineto(220, 140); // line to bottom-right corner ctx.closepath(); // line to bottom-left corner ctx.stroke(); result closing just one sub-path this example draws a smiley face consisting of three disconnected sub-p...
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.arc(240, 20, 40, 0, math.pi); ctx.moveto(100, 20); ctx.arc(60, 20, 40, 0, math.pi); ctx.moveto(215, 80); ctx.arc(150, 80, 65, 0, math.pi); ctx.closepath(); ctx.linewidth = 6; ctx.stroke(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.closepath' in that specification.

CanvasRenderingContext2D.createImageData() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const imagedata = ctx.createimagedata(100, 50); console.log(imagedata); // imagedata { width: 100, height: 50, data: uint8clampedarray[20000] } filling a blank imagedata object this example creates and fills a new imagedata object with purple pixels.
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const imagedata = ctx.createimagedata(100, 100); // iterate through every pixel for (let i = 0; i < imagedata.data.length; i += 4) { // modify pixel data imagedata.data[i + 0] = 190; // r value imagedata.data[i + 1] = 0; // g value imagedata.data[i + 2] = 210; // b value imagedata.data[i + 3] = 255; // a value } // draw image data to the canvas ctx.putimagedata(imagedata, 20, 20); result more examples for more examples using createimagedata() and the im...

CanvasRenderingContext2D.drawImage() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const image = document.getelementbyid('source'); image.addeventlistener('load', e => { ctx.drawimage(image, 33, 71, 104, 124, 21, 20, 87, 104); }); result understanding source element size the drawimage() method uses the source element's intrinsic size in css pixels when drawing.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const image = new image(60, 45); // using optional size for image image.onload = drawimageactualsize; // draw when image has loaded // load an image of intrinsic size 300x227 in css pixels image.src = 'https://udn.realityripple.com/samples/db/f374e9c6fc.jpg'; function drawimageactualsize() { // use the intrinsic size of image in css pixels for ...

CanvasRenderingContext2D.ellipse() - Web APIs
html <canvas id="canvas" width="200" height="200"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // draw the ellipse ctx.beginpath(); ctx.ellipse(100, 100, 50, 75, math.pi / 4, 0, 2 * math.pi); ctx.stroke(); // draw the ellipse's line of reflection ctx.beginpath(); ctx.setlinedash([5, 5]); ctx.moveto(0, 200); ctx.lineto(200, 0); ctx.stroke(); result various elliptical arcs this example creates three elliptical paths with varying propert...
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.fillstyle = 'red'; ctx.beginpath(); ctx.ellipse(60, 75, 50, 30, math.pi * .25, 0, math.pi * 1.5); ctx.fill(); ctx.fillstyle = 'blue'; ctx.beginpath(); ctx.ellipse(150, 75, 50, 30, math.pi * .25, 0, math.pi); ctx.fill(); ctx.fillstyle = 'green'; ctx.beginpath(); ctx.ellipse(240, 75, 50, 30, math.pi * .25, 0, math.pi, true); ctx.fill(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.ellipse' in that specification.

CanvasRenderingContext2D.fill() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.rect(10, 10, 150, 100); ctx.fill(); result specifying a path and a fillrule this example saves some intersecting lines to a path2d object.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // create path let region = new path2d(); region.moveto(30, 90); region.lineto(110, 20); region.lineto(240, 130); region.lineto(60, 130); region.lineto(190, 20); region.lineto(270, 90); region.closepath(); // fill path ctx.fillstyle = 'green'; ctx.fill(region, 'evenodd'); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.fill' in that specification.

CanvasRenderingContext2D.fillRect() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.fillstyle = 'green'; ctx.fillrect(20, 10, 150, 100); result filling the whole canvas this code snippet fills the entire canvas with a rectangle.
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.fillrect(0, 0, canvas.width, canvas.height); specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.fillrect' in that specification.

CanvasRenderingContext2D.fillStyle - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.fillstyle = 'blue'; ctx.fillrect(10, 10, 100, 100); result creating multiple fill colors using loops in this example, we use two for loops to draw a grid of rectangles, each having a different fill color.
... <canvas id="canvas" width="150" height="150"></canvas> const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); for (let i = 0; i < 6; i++) { for (let j = 0; j < 6; j++) { ctx.fillstyle = `rgb( ${math.floor(255 - 42.5 * i)}, ${math.floor(255 - 42.5 * j)}, 0)`; ctx.fillrect(j * 25, i * 25, 25, 25); } } the result looks like this: screenshotlive sample specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.fillsty...

CanvasRenderingContext2D.fillText() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = '50px serif'; ctx.filltext('hello world', 50, 90); this code obtains a reference to the <canvas>, then gets a reference to its 2d graphics context.
... html <canvas id="canvas" width="400" height="150"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = '50px serif'; ctx.filltext('hello world', 50, 90, 140); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.filltext' in that specification.

CanvasRenderingContext2D.filter - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.filter = 'blur(4px)'; ctx.font = '48px serif'; ctx.filltext('hello world', 50, 100); result applying multiple filters you can combine as many filters as you like.
... html <canvas id="canvas"></canvas> <div style="display:none;"> <img id="source" src="https://udn.realityripple.com/samples/90/a34a525ace.jpg"> </div> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const image = document.getelementbyid('source'); image.addeventlistener('load', e => { ctx.filter = 'contrast(1.4) sepia(1) drop-shadow(9px 9px 2px #e81)'; ctx.drawimage(image, 10, 10, 180, 120); }); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.filter' in that specification.

CanvasRenderingContext2D.globalAlpha - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.globalalpha = 0.5; ctx.fillstyle = 'blue'; ctx.fillrect(10, 10, 100, 100); ctx.fillstyle = 'red'; ctx.fillrect(50, 50, 100, 100); result overlaying transparent shapes this example illustrates the effect of overlaying multiple transparent shapes on top of each other.
... <canvas id="canvas" width="150" height="150"></canvas> const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // draw background ctx.fillstyle = '#fd0'; ctx.fillrect(0, 0, 75, 75); ctx.fillstyle = '#6c0'; ctx.fillrect(75, 0, 75, 75); ctx.fillstyle = '#09f'; ctx.fillrect(0, 75, 75, 75); ctx.fillstyle = '#f30'; ctx.fillrect(75, 75, 75, 75); ctx.fillstyle = '#fff'; // set transparency value ctx.globalalpha = 0.2; // draw transparent circles for (let i = 0; ...

CanvasRenderingContext2D.isPointInPath() - Web APIs
html <canvas id="canvas"></canvas> <p>in path: <code id="result">false</code></p> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const result = document.getelementbyid('result'); ctx.rect(10, 10, 100, 100); ctx.fill(); result.innertext = ctx.ispointinpath(30, 70); result checking a point in the specified path whenever you move the mouse, this example checks whether the cursor is in a circular path2d path.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // create circle const circle = new path2d(); circle.arc(150, 75, 50, 0, 2 * math.pi); ctx.fillstyle = 'red'; ctx.fill(circle); // listen for mouse moves canvas.addeventlistener('mousemove', function(event) { // check whether point is inside circle if (ctx.ispointinpath(circle, event.offsetx, event.offsety)) { ctx.fillstyle = 'green'; } else { ctx.fillstyle = 'red'; } // draw circle ctx.clearrect(0, 0, canvas.width, canvas.height); ctx.fill(circle); }); result specifications specification status comment html living standardthe definition of 'canvasrendering...

CanvasRenderingContext2D.isPointInStroke() - Web APIs
html <canvas id="canvas"></canvas> <p>in stroke: <code id="result">false</code></p> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const result = document.getelementbyid('result'); ctx.rect(10, 10, 100, 100); ctx.stroke(); result.innertext = ctx.ispointinstroke(50, 10); result checking a point in the specified path whenever you move the mouse, this example checks whether the cursor is in the stroke of an elliptical path2d path.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // create ellipse const ellipse = new path2d(); ellipse.ellipse(150, 75, 40, 60, math.pi * .25, 0, 2 * math.pi); ctx.linewidth = 25; ctx.strokestyle = 'red'; ctx.fill(ellipse); ctx.stroke(ellipse); // listen for mouse moves canvas.addeventlistener('mousemove', function(event) { // check whether point is inside ellipse's stroke if (ctx.ispointinstroke(ellipse, event.offsetx, event.offsety)) { ctx.strokestyle = 'green'; } else { ctx.strokestyle = 'red'; } // draw ellipse ctx.clearrect(0, 0, canvas.width, canvas.height); ctx.fill(ellipse); ctx.stroke(ellipse); }); result s...

CanvasRenderingContext2D.lineCap - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(20, 20); ctx.linewidth = 15; ctx.linecap = 'round'; ctx.lineto(100, 100); ctx.stroke(); result comparison of line caps in this example three lines are drawn, each with a different value for the linecap property.
... <canvas id="canvas" width="150" height="150"></canvas> const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const linecap = ['butt', 'round', 'square']; // draw guides ctx.strokestyle = '#09f'; ctx.beginpath(); ctx.moveto(10, 10); ctx.lineto(140, 10); ctx.moveto(10, 140); ctx.lineto(140, 140); ctx.stroke(); // draw lines ctx.strokestyle = 'black'; for (let i = 0; i < linecap.length; i++) { ctx.linewidth = 15; ctx.linecap = linecap[i]; ctx.beginpat...

CanvasRenderingContext2D.lineDashOffset - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.setlinedash([4, 16]); // dashed line with no offset ctx.beginpath(); ctx.moveto(0, 50); ctx.lineto(300, 50); ctx.stroke(); // dashed line with offset of 4 ctx.beginpath(); ctx.strokestyle = 'red'; ctx.linedashoffset = 4; ctx.moveto(0, 100); ctx.lineto(300, 100); ctx.stroke(); result the line with a dash offset is drawn in red.
... html <canvas id="canvas"></canvas> const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let offset = 0; function draw() { ctx.clearrect(0, 0, canvas.width, canvas.height); ctx.setlinedash([4, 2]); ctx.linedashoffset = -offset; ctx.strokerect(10, 10, 100, 100); } function march() { offset++; if (offset > 16) { offset = 0; } draw(); settimeout(march, 20); } march(); specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.linedashof...

CanvasRenderingContext2D.lineJoin - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.linewidth = 20; ctx.linejoin = 'round'; ctx.beginpath(); ctx.moveto(20, 20); ctx.lineto(190, 100); ctx.lineto(280, 20); ctx.lineto(280, 150); ctx.stroke(); result comparison of line joins the example below draws three different paths, demonstrating each of the three linejoin options.
... <canvas id="canvas" width="150" height="150"></canvas> var ctx = document.getelementbyid('canvas').getcontext('2d'); var linejoin = ['round', 'bevel', 'miter']; ctx.linewidth = 10; for (let i = 0; i < linejoin.length; i++) { ctx.linejoin = linejoin[i]; ctx.beginpath(); ctx.moveto(-5, 5 + i * 40); ctx.lineto(35, 45 + i * 40); ctx.lineto(75, 5 + i * 40); ctx.lineto(115, 45 + i * 40); ctx.lineto(155, 5 + i * 40); ctx.stroke(); } screenshotlive sample specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.linejoin' in that specification.

CanvasRenderingContext2D.lineTo() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); // start a new path ctx.moveto(30, 50); // move the pen to (30, 50) ctx.lineto(150, 100); // draw a line to (150, 100) ctx.stroke(); // render the path result drawing connected lines each call of lineto() (and similar methods) automatically adds to the current sub-path, which means that all the lines will al...
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.moveto(90, 130); ctx.lineto(95, 25); ctx.lineto(150, 80); ctx.lineto(205, 25); ctx.lineto(210, 130); ctx.linewidth = 15; ctx.stroke(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.lineto' in that specification.

CanvasRenderingContext2D.quadraticCurveTo() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // quadratic bézier curve ctx.beginpath(); ctx.moveto(50, 20); ctx.quadraticcurveto(230, 30, 50, 100); ctx.stroke(); // start and end points ctx.fillstyle = 'blue'; ctx.beginpath(); ctx.arc(50, 20, 5, 0, 2 * math.pi); // start point ctx.arc(50, 100, 5, 0, 2 * math.pi); // end point ctx.fill(); // control point ctx.fillstyle = 'red'; ctx.begin...
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(20, 110); ctx.quadraticcurveto(230, 150, 250, 20); ctx.stroke(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.quadraticcurveto' in that specification.

CanvasRenderingContext2D.resetTransform() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // draw a rotated rectangle ctx.rotate(45 * math.pi / 180); ctx.fillrect(60, 0, 100, 30); // reset transformation matrix to the identity matrix ctx.resettransform(); result continuing with a regular matrix whenever you're done drawing transformed shapes, you should call resettransform() before rendering anything else.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // skewed rectangles ctx.transform(1, 0, 1.7, 1, 0, 0); ctx.fillstyle = 'gray'; ctx.fillrect(40, 40, 50, 20); ctx.fillrect(40, 90, 50, 20); // non-skewed rectangles ctx.resettransform(); ctx.fillstyle = 'red'; ctx.fillrect(40, 40, 50, 20); ctx.fillrect(40, 90, 50, 20); result the skewed rectangles are gray, and the non-skewed rectangles are red.

CanvasRenderingContext2D.rotate() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // point of transform origin ctx.arc(0, 0, 5, 0, 2 * math.pi); ctx.fillstyle = 'blue'; ctx.fill(); // non-rotated rectangle ctx.fillstyle = 'gray'; ctx.fillrect(100, 0, 80, 20); // rotated rectangle ctx.rotate(45 * math.pi / 180); ctx.fillstyle = 'red'; ctx.fillrect(100, 0, 80, 20); // reset transformation matrix to the identity matrix ctx.settr...
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // non-rotated rectangle ctx.fillstyle = 'gray'; ctx.fillrect(80, 60, 140, 30); // matrix transformation ctx.translate(150, 75); ctx.rotate(math.pi / 2); ctx.translate(-150, -75); // rotated rectangle ctx.fillstyle = 'red'; ctx.fillrect(80, 60, 140, 30); result the non-rotated rectangle is gray, and the rotated rectangle is red.

CanvasRenderingContext2D.scale() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // scaled rectangle ctx.scale(9, 3); ctx.fillstyle = 'red'; ctx.fillrect(10, 10, 8, 20); // reset current transformation matrix to the identity matrix ctx.settransform(1, 0, 0, 1, 0, 0); // non-scaled rectangle ctx.fillstyle = 'gray'; ctx.fillrect(10, 10, 8, 20); result the scaled rectangle is red, and the non-scaled rectangle is gray.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.scale(-1, 1); ctx.font = '48px serif'; ctx.filltext('hello world!', -280, 90); ctx.settransform(1, 0, 0, 1, 0, 0); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.scale' in that specification.

CanvasRenderingContext2D.scrollPathIntoView() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.fillrect(10, 10, 30, 30); ctx.scrollpathintoview(); edit the code below to see your changes update live in the canvas: playable code <canvas id="canvas" width="400" height="200" class="playable-canvas"> <input id="button" type="range" min="1" max="12"> </canvas> <div class="playable-buttons"> <input id="edit" type="butto...
...n" value="edit" /> <input id="reset" type="button" value="reset" /> </div> <textarea id="code" class="playable-code"> ctx.beginpath(); ctx.rect(10, 10, 30, 30); ctx.scrollpathintoview();</textarea> var canvas = document.getelementbyid("canvas"); var ctx = canvas.getcontext("2d"); var textarea = document.getelementbyid("code"); var reset = document.getelementbyid("reset"); var edit = document.getelementbyid("edit"); var code = textarea.value; function drawcanvas() { ctx.clearrect(0, 0, canvas.width, canvas.height); eval(textarea.value); } reset.addeventlistener("click", function() { textarea.value = code; drawcanvas(); }); edit.addeventlistener("click", function() { textarea.focus(); }) textarea.addeventlistener("input", drawcanvas); window.addeventlistener("load", drawcanvas); spe...

CanvasRenderingContext2D.setLineDash() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // dashed line ctx.beginpath(); ctx.setlinedash([5, 15]); ctx.moveto(0, 50); ctx.lineto(300, 50); ctx.stroke(); // solid line ctx.beginpath(); ctx.setlinedash([]); ctx.moveto(0, 100); ctx.lineto(300, 100); ctx.stroke(); result some common patterns this example illustrates a variety of common line dash patterns.
... function drawdashedline(pattern) { ctx.beginpath(); ctx.setlinedash(pattern); ctx.moveto(0, y); ctx.lineto(300, y); ctx.stroke(); y += 20; } const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let y = 15; drawdashedline([]); drawdashedline([1, 1]); drawdashedline([10, 10]); drawdashedline([20, 5]); drawdashedline([15, 3, 3, 3]); drawdashedline([20, 3, 3, 3, 3, 3, 3, 3]); drawdashedline([12, 3, 3]); // equals [12, 3, 3, 12, 3, 3] result specifications specification status comment html living standardthe definition of 'canvasrende...

CanvasRenderingContext2D.shadowColor - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // shadow ctx.shadowcolor = 'red'; ctx.shadowoffsetx = 10; ctx.shadowoffsety = 10; // filled rectangle ctx.fillrect(20, 20, 100, 100); // stroked rectangle ctx.linewidth = 6; ctx.strokerect(170, 20, 100, 100); result shadows on translucent shapes a shadow's opacity is affected by the transparency level of its parent object (even when shadow...
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // shadow ctx.shadowcolor = 'rgba(255, 0, 0, .8)'; ctx.shadowblur = 8; ctx.shadowoffsetx = 30; ctx.shadowoffsety = 20; // filled rectangle ctx.fillstyle = 'rgba(0, 255, 0, .2)'; ctx.fillrect(10, 10, 150, 100); // stroked rectangle ctx.linewidth = 10; ctx.strokestyle = 'rgba(0, 0, 255, .6)'; ctx.strokerect(10, 10, 150, 100); result specifications specification status comment html living standardthe definition of '...

CanvasRenderingContext2D.strokeRect() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.strokestyle = 'green'; ctx.strokerect(20, 10, 160, 100); result applying various context settings this example draws a rectangle with a drop shadow and thick, beveled outlines.
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.shadowcolor = '#d53'; ctx.shadowblur = 20; ctx.linejoin = 'bevel'; ctx.linewidth = 15; ctx.strokestyle = '#38f'; ctx.strokerect(30, 30, 160, 90); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.strokerect' in that specification.

CanvasRenderingContext2D.strokeStyle - Web APIs
html <canvas id="canvas"></canvas> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.strokestyle = 'blue'; ctx.strokerect(10, 10, 100, 100); result creating multiple stroke colors using loops in this example, we use two for loops and the arc() method to draw a grid of circles, each having a different stroke color.
...(the red channel has a fixed value.) <canvas id="canvas" width="150" height="150"></canvas> var ctx = document.getelementbyid('canvas').getcontext('2d'); for (let i = 0; i < 6; i++) { for (let j = 0; j < 6; j++) { ctx.strokestyle = `rgb( 0, ${math.floor(255 - 42.5 * i)}, ${math.floor(255 - 42.5 * j)})`; ctx.beginpath(); ctx.arc(12.5 + j * 25, 12.5 + i * 25, 10, 0, math.pi * 2, true); ctx.stroke(); } } the result looks like this: screenshotlive sample specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.strokestyle' in that specificat...

CanvasRenderingContext2D.strokeText() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = '50px serif'; ctx.stroketext('hello world', 50, 90); this code obtains a reference to the <canvas>, then gets a reference to its 2d graphics context.
... html <canvas id="canvas" width="400" height="150"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = '50px serif'; ctx.stroketext('hello world', 50, 90, 140); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.stroketext' in that specification.

CanvasRenderingContext2D.textAlign - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); canvas.width = 350; const ctx = canvas.getcontext('2d'); const x = canvas.width / 2; ctx.beginpath(); ctx.moveto(x, 0); ctx.lineto(x, canvas.height); ctx.stroke(); ctx.font = '30px serif'; ctx.textalign = 'left'; ctx.filltext('left-aligned', x, 40); ctx.textalign = 'center'; ctx.filltext('center-aligned', x, 85); ctx.textalign = 'right'; ctx.filltext('right-aligned', x, 130); re...
... html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = '30px serif'; ctx.direction = 'ltr'; ctx.textalign = 'start'; ctx.filltext('start-aligned', 0, 50); ctx.textalign = 'end'; ctx.filltext('end-aligned', canvas.width, 120); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.textalign' in that specification.

Canvas API - Web APIs
html <canvas id="canvas"></canvas> javascript the document.getelementbyid() method gets a reference to the html <canvas> element.
... const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.fillstyle = 'green'; ctx.fillrect(10, 10, 150, 100); result reference htmlcanvaselement canvasrenderingcontext2d canvasgradient canvasimagesource canvaspattern imagebitmap imagedata renderingcontext textmetrics offscreencanvas path2d imagebitmaprenderingcontext note: the interfaces related to the webglrenderingcontext are ...

DataTransfer.clearData() - Web APIs
="status">drag to start</span></div> <div>data is: <span id="data">uninitialized</span></div> css span.tweaked { display: inline-block; margin: 1em 0; padding: 1em 2em; } #source { color: blue; border: 1px solid black; } #target { border: 1px solid black; } javascript window.addeventlistener('domcontentloaded', function () { // select html elements var draggable = document.getelementbyid('source'); var dropable = document.getelementbyid('target'); var status = document.getelementbyid('status'); var data = document.getelementbyid('data'); var dropped = false; // register event handlers draggable.addeventlistener('dragstart', dragstarthandler); draggable.addeventlistener('dragend', dragendhandler); dropable.addeventlistener('dragover', dragoverhandler); dropable.
...t(); } function dragleavehandler (event) { status.innerhtml = 'drag in process (drop was available)'; event.preventdefault(); } function drophandler (event) { dropped = true; status.innerhtml = 'drop done'; event.preventdefault(); // get data linked to event format « text » var _data = event.datatransfer.getdata('text/plain'); var element = document.getelementbyid(_data); // append drag source element to event's target element event.target.appendchild(element); // change css styles and displayed text element.style.csstext = 'border: 1px solid black;display: block; color: red'; element.innerhtml = "i'm in the drop zone!"; } }) specifications specification status comment html living standardthe definition ...

DocumentFragment - Web APIs
documentfragment.getelementbyid() returns the first element node within the documentfragment, in document order, that matches the specified id.
... functionally equivalent to document.getelementbyid().

Introduction to the DOM - Web APIs
const table = document.getelementbyid("table"); const tableattrs = table.attributes; // node/element interface for (let i = 0; i < tableattrs.length; i++) { // htmltableelement interface: border attribute if(tableattrs[i].nodename.tolowercase() == "border") table.border = "1"; } // htmltableelement interface: summary attribute table.summary = "note: increased border"; core interfaces in the dom this section lists some of t...
... document.getelementbyid(id) document.getelementsbytagname(name) document.createelement(name) parentnode.appendchild(node) element.innerhtml element.style.left element.setattribute() element.getattribute() element.addeventlistener() window.content window.onload window.scrollto() testing the dom api this document provides samples for every interface that you can use in your own web development.

Element.getAttributeNS() - Web APIs
<svg xmlns="http://www.w3.org/2000/svg" xmlns:test="http://www.example.com/2014/test" width="40" height="40"> <circle id="target" cx="12" cy="12" r="10" stroke="#444" stroke-width="2" fill="none" test:foo="hello namespaced attribute!"/> <script type="text/javascript"> var ns = 'http://www.example.com/2014/test'; var circle = document.getelementbyid( 'target' ); console.log( 'attribute test:foo: "' + circle.getattributens( ns, 'foo' ) + '"' ); </script> </svg> in an html5 document the attribute has to be accessed with test:foo since namespaces are not supported.
... <!doctype html> <html> <body> <svg xmlns="http://www.w3.org/2000/svg" xmlns:test="http://www.example.com/2014/test" width="40" height="40"> <circle id="target" cx="12" cy="12" r="10" stroke="#444" stroke-width="2" fill="none" test:foo="foo value"/> </svg> <script type="text/javascript"> var ns = 'http://www.example.com/2014/test'; var circle = document.getelementbyid( 'target' ); console.log('attribute value: ' + circle.getattribute('test:foo')); </script> </body> </html> notes namespaces are only supported in xml documents.

Element.hasPointerCapture() - Web APIs
examples <html> <script> function downhandler(ev) { const el = document.getelementbyid("target"); // element 'target' will receive/capture further events el.setpointercapture(ev.pointerid); /* ...
... } } function init() { const el = document.getelementbyid("target"); el.onpointerdown = downhandler; } </script> <body onload="init();"> <div id="target">touch this element with a pointer.</div> </body> </html> specifications specification status comment pointer events – level 2the definition of 'haspointercapture()' in that specification.

Element.scrollHeight - Web APIs
dius: 5px; width: 600px; padding: 5px; border: 2px #7fdf55 solid; } #rules { width: 600px; height: 130px; padding: 5px; border: #2a9f00 solid 2px; border-radius: 5px; } javascript function checkreading () { if (checkreading.read) { return; } checkreading.read = this.scrollheight - this.scrolltop === this.clientheight; document.registration.accept.disabled = document.getelementbyid("nextstep").disabled = !checkreading.read; checkreading.noticebox.innerhtml = checkreading.read ?
... "thank you." : "please, scroll and read the following text."; } onload = function () { var otoberead = document.getelementbyid("rules"); checkreading.noticebox = document.createelement("span"); document.registration.accept.checked = false; checkreading.noticebox.id = "notice"; otoberead.parentnode.insertbefore(checkreading.noticebox, otoberead); otoberead.parentnode.insertbefore(document.createelement("br"), otoberead); otoberead.onscroll = checkreading; checkreading.call(otoberead); } specifications specification status comment css object model (cssom) view modulethe definition of 'element.scrollheight' in that specification.

Element.setCapture() - Web APIs
<html> <head> <title>mouse capture example</title> <style type="text/css"> #mybutton { border: solid black 1px; color: black; padding: 2px; box-shadow: black 2px 2px; } </style> <script type="text/javascript"> function init() { var btn = document.getelementbyid("mybutton"); if (btn.setcapture) { btn.addeventlistener("mousedown", mousedown, false); btn.addeventlistener("mouseup", mouseup, false); } else { document.getelementbyid("output").innerhtml = "sorry, there appears to be no setcapture support on this browser"; } } function mousedown(e) { e.target.setcapture(); e.target.addeve...
...ntlistener("mousemove", mousemoved, false); } function mouseup(e) { e.target.removeeventlistener("mousemove", mousemoved, false); } function mousemoved(e) { var output = document.getelementbyid("output"); output.innerhtml = "position: " + e.clientx + ", " + e.clienty; } </script> </head> <body onload="init()"> <p>this is an example of how to use mouse capture on elements in gecko 2.0.</p> <p><a id="mybutton" href="#">test me</a></p> <div id="output">no events yet</div> </body> </html> view live examples notes the element may not be scrolled completely to the top or bottom, depending on the layout of other elements.

Comparison of Event Targets - Web APIs
> </thead> <tr> <td id="target"></td> <td id="currenttarget"></td> <td id="relatedtarget"></td> <td id="explicitoriginaltarget"></td> <td id="originaltarget"></td> </tr> </table> <p>clicking on the text will show the difference between explicitoriginaltarget, originaltarget, and target</p> <script> function handleclicks(e) { document.getelementbyid('target').innerhtml = e.target; document.getelementbyid('currenttarget').innerhtml = e.currenttarget; document.getelementbyid('relatedtarget').innerhtml = e.relatedtarget; document.getelementbyid('explicitoriginaltarget').innerhtml = e.explicitoriginaltarget; document.getelementbyid('originaltarget').innerhtml = e.originaltarget; } function handlemouseover...
...(e) { document.getelementbyid('target').innerhtml = e.target; document.getelementbyid('relatedtarget').innerhtml = e.relatedtarget; } document.addeventlistener('click', handleclicks, false); document.addeventlistener('mouseover', handlemouseover, false); </script> </body> </html> use of target and relatedtarget the relatedtarget property for the mouseover event holds the node that the mouse was previously over.

Event.preventDefault() - Web APIs
this example demonstrates how to prevent that from happening: javascript document.queryselector("#id-checkbox").addeventlistener("click", function(event) { document.getelementbyid("output-box").innerhtml += "sorry!
...first, listen for keypress events: var mytextbox = document.getelementbyid('my-textbox'); mytextbox.addeventlistener('keypress', checkname, false); the checkname() function, which looks at the pressed key and decides whether to allow it: function checkname(evt) { var charcode = evt.charcode; if (charcode != 0) { if (charcode < 97 || charcode > 122) { evt.preventdefault(); displaywarning( "please use lowercase letters only." + "\n" ...

FileList - Web APIs
for example, if the html includes the following file input: <input id="fileitem" type="file"> the following line of code fetches the first file in the node's file list as a file object: var file = document.getelementbyid('fileitem').files[0]; method overview file item(index); properties attribute type description length integer a read-only value indicating the number of files in the list.
... example this example iterates over all the files selected by the user using an input element: // fileinput is an html input element: <input type="file" id="myfileinput" multiple> var fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (similar to nodelist) var files = fileinput.files; var file; // loop through files for (var i = 0; i < files.length; i++) { // get item file = files.item(i); //or file = files[i]; alert(file.name); } here is a complete example.

GlobalEventHandlers.onanimationcancel - Web APIs
function log(msg, event) { let logbox = document.getelementbyid("log"); logbox.innerhtml += msg; if (event) { logbox.innerhtml += " <code>"+ event.animationname + "</code> at time " + event.elapsedtime.tofixed(2) + " seconds."; } logbox.innerhtml += "\n"; }; then we set up the handlecancelevent() function, which is called in response to the animationcancel event, as set up in the html above.
... function handlecancelevent(event) { log("animation canceled", event); }; then we add a method to handle toggle display between "flex" and "none" and establish it as the handler for a click event on the "hide/show" the box button: document.getelementbyid('togglebox').addeventlistener('click', function() { if (box.style.display == "none") { box.style.display = "flex"; document.getelementbyid("togglebox").innerhtml = "hide the box"; } else { box.style.display = "none"; document.getelementbyid("togglebox").innerhtml = "show the box"; } }); toggling the box to display: none has the effect of aborting its animation.

GlobalEventHandlers.onanimationend - Web APIs
function log(msg, event) { let logbox = document.getelementbyid("log"); logbox.innerhtml += msg; if (event) { logbox.innerhtml += " <code>"+ event.animationname + "</code> at time " + event.elapsedtime.tofixed(2) + " seconds."; } logbox.innerhtml += "\n"; }; then we set up the event handlers for the animationstart and animationend events: let box = document.getelementbyid("box"); box.onanimationstart = function(event) { lo...
...g("animation started", event); } box.onanimationend = function(event) { log("animation stopped", event); }; finally, we set up a handler for a click on the button that runs the animation: document.getelementbyid("play").addeventlistener("click", function(event) { document.getelementbyid("box").classname = "slideanimation"; event.target.style.display = "none"; }, false); this sets the class of the box we want to animate to the class that contains the animation description, then hides the play button because this example will only run the animation once.

GlobalEventHandlers.onanimationiteration - Web APIs
var box = document.getelementbyid("box"); var iterationcounter = 0; box.onanimationiteration = function(event) { box.style.animationplaystate = "paused"; document.getelementbyid("play").innerhtml = "start iteration #" + (iterationcounter+1); }; this sets up two global variables: box, which references the "box" element that we're animating, and iterationcounter, which is initially zero, which indicates how many iterations o...
... finally, we set up a handler for a click on the button that runs the animation: document.getelementbyid("play").addeventlistener("click", function(event) { box.style.animationplaystate = "running"; iterationcounter++; }, false); this sets the box element's animation-play-state to "running" and increments the iteration counter.

GlobalEventHandlers.onanimationstart - Web APIs
function log(msg, event) { let logbox = document.getelementbyid("log"); logbox.innerhtml += msg; if (event) { logbox.innerhtml += " <code>"+ event.animationname + "</code> at time " + event.elapsedtime.tofixed(2) + " seconds."; } logbox.innerhtml += "\n"; }; then we set up the event handlers for the animationstart and animationend events: let box = document.getelementbyid("box"); box.onanimationstart = function(event) { lo...
...g("animation started", event); } box.onanimationend = function(event) { log("animation stopped", event); }; finally, we set up a handler for a click on the button that runs the animation: document.getelementbyid("play").addeventlistener("click", function(event) { document.getelementbyid("box").classname = "slideanimation"; event.target.style.display = "none"; }, false); this sets the class of the box we want to animate to the class that contains the animation description, then hides the play button because this example will only run the animation once.

GlobalEventHandlers.onclick - Web APIs
html <div id="demo">click here</div> javascript document.getelementbyid('demo').onclick = function changecontent() { document.getelementbyid('demo').innerhtml = "help me"; document.getelementbyid('demo').style = "color: red"; } result getting the coordinates of clicks this example displays the coordinates at which the most recent mouse button click occurred.
... html <p>click anywhere in this example.</p> <p id="log"></p> javascript let log = document.getelementbyid('log'); document.onclick = inputchange; function inputchange(e) { log.textcontent = `position: (${e.clientx}, ${e.clienty})`; } result specification specification status comment html living standardthe definition of 'onclick' in that specification.

GlobalEventHandlers.ondragend - Web APIs
etdata("text", ev.target.id); } function dragover_handler(ev) { console.log("dragover"); // change the target element's border to signify a drag over event // has occurred ev.currenttarget.style.background = "lightblue"; ev.preventdefault(); } function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragenter_handler(ev) { console.log("dragenter"); // change the source element's background color for enter events ev.currenttarget.style.background = "yellow"; } function dragleave_handler(ev) { console.log("dragleave"); // change the source element's border back to white ev.currenttarget.style.background = "white"; } function dragend_handler(ev) { console.log("drage...
... var el=document.getelementbyid("target"); el.style.background = "pink"; } function dragexit_handler(ev) { console.log("dragexit"); // change the source element's border back to green to signify a dragexit event ev.currenttarget.style.background = "green"; } function init() { // set handlers for the source's enter/leave/end/exit events var el=document.getelementbyid("source"); el.ondragenter = dragenter_handler; el.ondragleave = dragleave_handler; el.ondragend = dragend_handler; el.ondragexit = dragexit_handler; } </script> <body onload="init();"> <h1>examples of <code>ondragenter</code>, <code>ondragleave</code>, <code>ondragend</code>, <code>ondragexit</code></h1> <div> <p id="source" ondrag...

GlobalEventHandlers.ondragenter - Web APIs
etdata("text", ev.target.id); } function dragover_handler(ev) { console.log("dragover"); // change the target element's border to signify a drag over event // has occurred ev.currenttarget.style.background = "lightblue"; ev.preventdefault(); } function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragenter_handler(ev) { console.log("dragenter"); // change the source element's background color for enter events ev.currenttarget.style.background = "yellow"; } function dragleave_handler(ev) { console.log("dragleave"); // change the source element's border back to white ev.currenttarget.style.background = "white"; } function dragend_handler(ev) { console.log("drage...
... var el=document.getelementbyid("target"); el.style.background = "pink"; } function dragexit_handler(ev) { console.log("dragexit"); // change the source element's border back to green to signify a dragexit event ev.currenttarget.style.background = "green"; } function init() { // set handlers for the source's enter/leave/end/exit events var el=document.getelementbyid("source"); el.ondragenter = dragenter_handler; el.ondragleave = dragleave_handler; el.ondragend = dragend_handler; el.ondragexit = dragexit_handler; } </script> <body onload="init();"> <h1>examples of <code>ondragenter</code>, <code>ondragleave</code>, <code>ondragend</code>, <code>ondragexit</code></h1> <div> <p id="source" ondrag...

GlobalEventHandlers.ondragexit - Web APIs
etdata("text", ev.target.id); } function dragover_handler(ev) { console.log("dragover"); // change the target element's border to signify a drag over event // has occurred ev.currenttarget.style.background = "lightblue"; ev.preventdefault(); } function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragenter_handler(ev) { console.log("dragenter"); // change the source element's background color for enter events ev.currenttarget.style.background = "yellow"; } function dragleave_handler(ev) { console.log("dragleave"); // change the source element's border back to white ev.currenttarget.style.background = "white"; } function dragend_handler(ev) { console.log("drage...
... var el=document.getelementbyid("target"); el.style.background = "pink"; } function dragexit_handler(ev) { console.log("dragexit"); // change the source element's border back to green to signify a dragexit event ev.currenttarget.style.background = "green"; } function init() { // set handlers for the source's enter/leave/end/exit events var el=document.getelementbyid("source"); el.ondragenter = dragenter_handler; el.ondragleave = dragleave_handler; el.ondragend = dragend_handler; el.ondragexit = dragexit_handler; } </script> <body onload="init();"> <h1>examples of <code>ondragenter</code>, <code>ondragleave</code>, <code>ondragend</code>, <code>ondragexit</code></h1> <div> <p id="source" ondrag...

GlobalEventHandlers.ondragleave - Web APIs
xt", ev.target.id); } function dragover_handler(ev) { console.log("dragover"); // change the target element's background color to signify a drag over event // has occurred ev.currenttarget.style.background = "lightblue"; ev.preventdefault(); } function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragenter_handler(ev) { console.log("dragenter"); // change the source element's background color for enter events ev.currenttarget.style.background = "yellow"; } function dragleave_handler(ev) { console.log("dragleave"); // change the source element's background color back to white ev.currenttarget.style.background = "white"; } function dragend_handler(ev) { console.
... var el=document.getelementbyid("target"); el.style.background = "pink"; } function dragexit_handler(ev) { console.log("dragexit"); // change the source element's background color back to green to signify a dragexit event ev.currenttarget.style.background = "green"; } function init() { // set handlers for the source's enter/leave/end/exit events var el=document.getelementbyid("source"); el.ondragenter = dragenter_handler; el.ondragleave = dragleave_handler; el.ondragend = dragend_handler; el.ondragexit = dragexit_handler; } </script> <body onload="init();"> <h1>examples of <code>ondragenter</code>, <code>ondragleave</code>, <code>ondragend</code>, <code>ondragexit</code></h1> <div> <...

HTMLElement.offsetLeft - Web APIs
example var colortable = document.getelementbyid("t1"); var toleft = colortable.offsetleft; if (toleft > 5) { // large left offset: do something here } this example shows a 'long' sentence that wraps within a div with a blue border, and a red box that one might think should describe the boundaries of the span.
...</span> <span id="longspan">long span that wraps within this div.</span> </div> <div id="box" style="position: absolute; border-color: red; border-width: 1; border-style: solid; z-index: 10"> </div> <script type="text/javascript"> var box = document.getelementbyid("box"); var longspan = document.getelementbyid("longspan"); box.style.left = longspan.offsetleft + document.body.scrollleft + "px"; box.style.top = longspan.offsettop + document.body.scrolltop + "px"; box.style.width = longspan.offsetwidth + "px"; box.style.height = longspan.offsetheight + "px"; </script> specification specification status comment css object model (cssom) view modulethe defin...

HTMLFormElement.elements - Web APIs
<form id="my-form"> <input type="text" name="username"> <input type="text" name="full-name"> <input type="password" name="password"> </form> var inputs = document.getelementbyid("my-form").elements; var inputbyindex = inputs[0]; var inputbyname = inputs["username"]; accessing form controls this example gets the form's element list, then iterates over the list, looking for <input> elements of type "text" so that some form of processing can be performed on them.
... var inputs = document.getelementbyid("my-form").elements; // iterate over the form controls for (i = 0; i < inputs.length; i++) { if (inputs[i].nodename === "input" && inputs[i].type === "text") { // update text input inputs[i].value.tolocaleuppercase(); } } disabling form controls var inputs = document.getelementbyid("my-form").elements; // iterate over the form controls for (i = 0; i < inputs.length; i++) { // disable all form controls inputs[i].setattribute("disabled", ""); } specifications specification status comment html living standardthe definition of 'htmlformelement.elements' in that specification.

HTMLElement.focus() - Web APIs
examples focus on a text field javascript focusmethod = function getfocus() { document.getelementbyid("mytextfield").focus(); } html <input type="text" id="mytextfield" value="text field."> <p></p> <button type="button" onclick="focusmethod()">click me to focus on the text field!</button> result focus on a button javascript focusmethod = function getfocus() { document.getelementbyid("mybutton").focus(); } html <button type="button" id="mybutton">click me!</button> <p></p> ...
...<button type="button" onclick="focusmethod()">click me to focus on the button!</button> result focus with focusoption javascript focusscrollmethod = function getfocus() { document.getelementbyid("mybutton").focus({preventscroll:false}); } focusnoscrollmethod = function getfocuswithoutscrolling() { document.getelementbyid("mybutton").focus({preventscroll:true}); } html <button type="button" onclick="focusscrollmethod()">click me to focus on the button!</button> <button type="button" onclick="focusnoscrollmethod()">click me to focus on the button without scrolling!</button> <div id="container" style="height: 1000px; width: 1000px;"> <button type="button" id="mybutton" style="margin-top: 500px;">click me!</button> </div> result specification specificatio...

HTMLSelectElement.add() - Web APIs
append to an existing collection var sel = document.getelementbyid("existinglist"); var opt = document.createelement("option"); opt.value = "3"; opt.text = "option: value 3"; sel.add(opt, null); /* takes the existing following select object: <select id="existinglist"> <option value="1">option: value 1</option> <option value="2">option: value 2</option> </select> and changes it to: <select id="existinglist"> <option value="1">option: v...
... inserting to an existing collection var sel = document.getelementbyid("existinglist"); var opt = document.createelement("option"); opt.value = "3"; opt.text = "option: value 3"; sel.add(opt, sel.options[1]); /* takes the existing following select object: <select id="existinglist"> <option value="1">option: value 1</option> <option value="2">option: value 2</option> </select> and changes it to: <select id="existinglist"> <option value="1">option: value 1</option> <option value="3">option: value 3</option> <option value="2">option: value 2</option> </sele...

HTMLTableElement.insertRow() - Web APIs
to insert the row into a specific <tbody>: let specific_tbody = document.getelementbyid(tbody_id); let row = specific_tbody.insertrow(index) note: insertrow() inserts the row directly into the table.
... html <table id="my-table"> <tr><td>row 1</td></tr> <tr><td>row 2</td></tr> <tr><td>row 3</td></tr> </table> javascript function addrow(tableid) { // get a reference to the table let tableref = document.getelementbyid(tableid); // insert a row at the end of the table let newrow = tableref.insertrow(-1); // insert a cell in the row at index 0 let newcell = newrow.insertcell(0); // append a text node to the cell let newtext = document.createtextnode('new bottom row'); newcell.appendchild(newtext); } // call addrow() with the table's id addrow('my-table'); result specifications spe...

The HTML DOM API - Web APIs
javascript const namefield = document.getelementbyid("username"); const sendbutton = document.getelementbyid("sendbutton") sendbutton.disabled = true; // [note: this is disabled since it causes this article to always load with this example focused and scrolled into view] //namefield.focus(); namefield.addeventlistener("input", event => { const elem = event.target; const valid = elem.value.length != 0; if (valid && sendbutton.disabled) { ...
... sendbutton.disabled = false; } else if (!valid && !sendbutton.disabled) { sendbutton.disabled = true; } }); this code uses the document interface's getelementbyid() method to get the dom object representing the <input> elements whose ids are username and sendbutton.

IntersectionObserver.unobserve() - Web APIs
var observer = new intersectionobserver(callback); observer.observe(document.getelementbyid("elementtoobserve")); /* ...
... */ observer.unobserve(document.getelementbyid("elementtoobserve")); specifications specification status comment intersection observerthe definition of 'intersectionobserver.unobserve()' in that specification.

KeyboardEvent.code - Web APIs
code values are for each one.</p> <div id="output"> </div> css #output { font-family: arial, helvetica, sans-serif; border: 1px solid black; } javascript window.addeventlistener("keydown", function(event) { let str = "keyboardevent: key='" + event.key + "' | code='" + event.code + "'"; let el = document.createelement("span"); el.innerhtml = str + "<br/>"; document.getelementbyid("output").appendchild(el); }, true); try it out to ensure that keystrokes go to the sample, click in the output box below before pressing keys.
... let shipsize = { width: 30, height: 30 }; let position = { x: 200, y: 200 }; let moverate = 9; let turnrate = 5; let angle = 0; let spaceship = document.getelementbyid("spaceship"); next comes the function updateposition().

KeyframeEffect.target - Web APIs
syntax var targetelement = document.getelementbyid("elementtoanimate"); var keyframes = new keyframeeffect( targetelement, keyframeblock, timingoptions ); // returns #elementtoanimate keyframes.target; // assigns keyframes a new target keyframes.target = newtargetelement; value an element, csspseudoelement, or null.
... examples in the follow the white rabbit example, whiterabbit sets the target element to be animated: var whiterabbit = document.getelementbyid("rabbit"); var rabbitdownkeyframes = new keyframeeffect( whiterabbit, [ { transform: 'translatey(0%)' }, { transform: 'translatey(100%)' } ], { duration: 3000, fill: 'forwards' } ); // returns <div id=​"rabbit">​click the rabbit's ears!​</div>​ rabbitdownkeyframes.target; specifications specification status comment web animationsthe definition of 'keyframeeffect' in that specification.

MediaDevices.ondevicechange - Web APIs
let videoelement = document.getelementbyid("video"); let logelement = document.getelementbyid("log"); function log(msg) { logelement.innerhtml += msg + "<br>"; } document.getelementbyid("startbutton").addeventlistener("click", function() { navigator.mediadevices.getusermedia({ video: { width: 160, height: 120, framerate: 30 }, audio: { samplerate: 44100, samplesize: 16, volume: 0.25 ...
... } }).then(stream => { videoelement.srcobject = stream; updatedevicelist(); }) .catch(err => log(err.name + ": " + err.message)); }, false); we set up global variables that contain references to the <ul> elements that are used to list the audio and video devices: let audiolist = document.getelementbyid("audiolist"); let videolist = document.getelementbyid("videolist"); getting and drawing the device list now let's take a look at updatedevicelist() itself.

MediaStreamConstraints.audio - Web APIs
css content body { font: 14px "open sans", "arial", sans-serif; } audio { margin-top: 20px; border: 1px solid black; width: 160px; } .button { cursor: pointer; width: 160px; border: 1px solid black; font-size: 16px; text-align: center; padding-top: 2px; padding-bottom: 4px; color: white; background-color: darkgreen; } javascript content let audioelement = document.getelementbyid("audio"); let logelement = document.getelementbyid("log"); function log(msg) { logelement.innerhtml += msg + "<br>"; } document.getelementbyid("startbutton").addeventlistener("click", function() { navigator.mediadevices.getusermedia({ audio: true }).then(stream => audioelement.srcobject = stream) .catch(err => log(err.name + ": " + err.message)); }, false); here we see an event ...
... css content body { font: 14px "open sans", "arial", sans-serif; } audio { margin-top: 20px; border: 1px solid black; width: 160px; } .button { cursor: pointer; width: 160px; border: 1px solid black; font-size: 16px; text-align: center; padding-top: 2px; padding-bottom: 4px; color: white; background-color: darkgreen; } javascript content let audioelement = document.getelementbyid("audio"); let logelement = document.getelementbyid("log"); function log(msg) { logelement.innerhtml += msg + "<br>"; } document.getelementbyid("startbutton").addeventlistener("click", function() { navigator.mediadevices.getusermedia({ audio: { samplesize: 8, echocancellation: true } }).then(stream => audioelement.srcobject = stream) .catch(err => log(err.name + ":...

MediaStreamConstraints.video - Web APIs
id="log"></div> css content body { font: 14px "open sans", "arial", sans-serif; } video { margin-top: 20px; border: 1px solid black; } .button { cursor: pointer; width: 160px; border: 1px solid black; font-size: 16px; text-align: center; padding-top: 2px; padding-bottom: 4px; color: white; background-color: darkgreen; } javascript content let videoelement = document.getelementbyid("video"); let logelement = document.getelementbyid("log"); function log(msg) { logelement.innerhtml += msg + "<br>"; } document.getelementbyid("startbutton").addeventlistener("click", function() { navigator.mediadevices.getusermedia({ video: true }).then(stream => videoelement.srcobject = stream) .catch(err => log(err.name + ": " + err.message)); }, false); here we see an even...
... id="log"></div> css content body { font: 14px "open sans", "arial", sans-serif; } video { margin-top: 20px; border: 1px solid black; } .button { cursor: pointer; width: 160px; border: 1px solid black; font-size: 16px; text-align: center; padding-top: 2px; padding-bottom: 4px; color: white; background-color: darkgreen; } javascript content let videoelement = document.getelementbyid("video"); let logelement = document.getelementbyid("log"); function log(msg) { logelement.innerhtml += msg + "<br>"; } document.getelementbyid("startbutton").addeventlistener("click", function() { navigator.mediadevices.getusermedia({ video: { width: 160, height: 120, framerate: 15 } }).then(stream => videoelement.srcobject = stream) .catch(err => ...

MediaStreamTrack: mute event - Web APIs
musictrack.addeventlistener("mute", event => { document.getelementbyid("timeline-widget").style.backgroundcolor = "#aaa"; }, false); musictrack.addeventlistener("unmute", event => { document.getelementbyid("timeline-widget").style.backgroundcolor = "#fff"; }, false); with these event handlers in place, when the track musictrack enters its muted state, the element with the id timeline-widget gets its background color changed to #aaa.
...the following example shows this: musictrack.onmute = event => { document.getelementbyid("timeline-widget").style.backgroundcolor = "#aaa"; } musictrack.mute = event = > { document.getelementbyid("timeline-widget").style.backgroundcolor = "#fff"; } specifications specification status comment media capture and streamsthe definition of 'mute' in that specification.

MediaStreamTrack: unmute event - Web APIs
musictrack.addeventlistener("mute", event => { document.getelementbyid("timeline-widget").style.backgroundcolor = "#aaa"; }, false); musictrack.addeventlistener("unmute", event => { document.getelementbyid("timeline-widget").style.backgroundcolor = "#fff"; }, false); with these event handlers in place, when the track musictrack enters its muted state, the element with the id timeline-widget gets its background color changed to #aaa.
...the following example shows this: musictrack.onmute = event => { document.getelementbyid("timeline-widget").style.backgroundcolor = "#aaa"; } musictrack.mute = event = > { document.getelementbyid("timeline-widget").style.backgroundcolor = "#fff"; } specifications specification status comment media capture and streamsthe definition of 'unmute' in that specification.

Using the Media Capabilities API - Web APIs
tion> <option>2500</option> <option>800</option> </select> </li> </ul> <p><input type="button" value="test this video configuration" id="tryit"></p> </form> <ul id="results"></ul> javascript let mc = { videoconfiguration : new object(), tryit: function () { mc.createconfiguration(); mc.testit(); }, createconfiguration: function () { var size = document.getelementbyid('size').value.split('x'); mc.videoconfiguration = { type: 'file', video: { contenttype: document.getelementbyid('codec').value, width: size[0], height: size[1], bitrate: document.getelementbyid('bitrate').value, framerate: document.getelementbyid('framerate').value, } } }, testit: function () { let content = ''; naviga...
...' is ' : ' is not ') + 'power efficient.'; var ul = document.getelementbyid("results") li.innerhtml = content; ul.appendchild(li); }).catch((error) => { var li = document.createelement('li'), ul = document.getelementbyid("results"); li.innertext = 'codec ' + mc.videoconfiguration.video.contenttype + ' threw an error: ' + error; ul.appendchild(li); }); } } document.getelementbyid('tryit').addeventlistener('click',...

Node.firstChild - Web APIs
<p id="para-01"> <span>first span</span> </p> <script> var p01 = document.getelementbyid('para-01'); console.log(p01.firstchild.nodename); </script> in the above, the console will show '#text' because a text node is inserted to maintain the whitespace between the end of the opening <p> and <span> tags.
... <p id="para-01"><span>first span</span></p> <script> var p01 = document.getelementbyid('para-01'); console.log(p01.firstchild.nodename); </script> now the console will show 'span'.

Node.removeChild() - Web APIs
examples simple examples given this html: <div id="top"> <div id="nested"></div> </div> to remove a specified element when knowing its parent node: let d = document.getelementbyid("top"); let d_nested = document.getelementbyid("nested"); let throwawaynode = d.removechild(d_nested); to remove a specified element without having to specify its parent node: let node = document.getelementbyid("nested"); if (node.parentnode) { node.parentnode.removechild(node); } to remove all children from an element: let element = document.getelementbyid("top"); while (element.firstchi...
...ld) { element.removechild(element.firstchild); } causing a typeerror <!--sample html code--> <div id="top"> </div> <script type="text/javascript"> let top = document.getelementbyid("top"); let nested = document.getelementbyid("nested"); // throws uncaught typeerror let garbage = top.removechild(nested); </script> causing a notfounderror <!--sample html code--> <div id="top"> <div id="nested"></div> </div> <script type="text/javascript"> let top = document.getelementbyid("top"); let nested = document.getelementbyid("nested"); // this first call correctly removes the node let garbage = top.removechild(nested); // throws uncaught notfounderror garbage = top.removechild(nested); </script> specifications specification status comment domthe def...

Node.textContent - Web APIs
you can use textcontent to get the element's text content: let text = document.getelementbyid('diva').textcontent; // the text variable is now: 'this is some text!' ...
... or set the element's text content: document.getelementbyid('diva').textcontent = 'this text is different!'; // the html for diva is now: // <div id="diva">this text is different!</div> specifications specification status comment domthe definition of 'node.textcontent' in that specification.

OffscreenCanvas - Web APIs
var one = document.getelementbyid("one").getcontext("bitmaprenderer"); var two = document.getelementbyid("two").getcontext("bitmaprenderer"); var offscreen = new offscreencanvas(256, 256); var gl = offscreen.getcontext('webgl'); // ...
... main.js (main thread code): var htmlcanvas = document.getelementbyid("canvas"); var offscreen = htmlcanvas.transfercontroltooffscreen(); var worker = new worker("offscreencanvas.js"); worker.postmessage({canvas: offscreen}, [offscreen]); offscreencanvas.js (worker code): onmessage = function(evt) { var canvas = evt.data.canvas; var gl = canvas.getcontext("webgl"); // ...

Path2D() - Web APIs
<canvas id="canvas"></canvas> const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let path1 = new path2d(); path1.rect(10, 10, 100,100); let path2 = new path2d(path1); path2.moveto(220, 60); path2.arc(170, 60, 50, 0, 2 * math.pi); ctx.stroke(path2); using svg paths this example creates a path2d path using svg path data.
... <canvas id="canvas"></canvas> const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let p = new path2d('m10 10 h 80 v 80 h -80 z'); ctx.fill(p); specification specification status comment html living standardthe definition of 'path2d()' in that specification.

RTCIceTransport: selectedcandidatepairchange event - Web APIs
let icetransport = pc.getsenders[0].transport.icetransport; let localprotoelem = document.getelementbyid("local-protocol"); let remoteprotoelem = document.getelementbyid("remote-protocol"); icetransport.addeventlistener("selectedcandidatepairchange", ev => { let pair = icetransport.getselectedcandidatepair(); localprotoelem.innertext = pair.local.protocol.touppercase(); remoteprotoelem.innertext = pair.remote.protocol.touppercase(); }, false) this can also be done by setting the onselectedca...
... let icetransport = pc.getsenders[0].transport.icetransport; let localprotoelem = document.getelementbyid("local-protocol"); let remoteprotoelem = document.getelementbyid("remote-protocol"); icetransport.onselectedcandidatepairchange = ev => { let pair = icetransport.getselectedcandidatepair(); localprotoelem.innertext = pair.local.protocol.touppercase(); remoteprotoelem.innertext = pair.remote.protocol.touppercase(); } specifications specification status comment webrtc 1.0: real-time communication between browsersthe definition of 'selectedcandidatepairchange' in that specification.

Range.setStart() - Web APIs
main st.<br> dodge city, ks<br> 67801<br> usa</p> <hr> <p>nodes in the original address:</p> <ol id="log"></ol> javascript const address = document.getelementbyid('address'); const log = document.getelementbyid('log'); // log info address.childnodes.foreach(node => { const li = document.createelement('li'); li.textcontent = `${node.nodename}, ${node.nodevalue}`; log.appendchild(li); }); // highlight the street and city const startoffset = 2; // start at third node: 101 e.
... html <p id="content">0123456789</p> <p id="log"></p> javascript const element = document.getelementbyid('content'); const textnode = element.childnodes[0]; const range = document.createrange(); range.setstart(textnode, 0); // start at first character range.setend(textnode, 5); // end at fifth character document.getelementbyid('log').textcontent = range; result specifications specification status comment domthe definition of 'range.setstart()' in that specification.

Response.redirected - Web APIs
fetch("awesome-picture.jpg").then(function(response) { let elem = document.getelementbyid("warning-message-box"); if (response.redirected) { elem.innerhtml = "unexpected redirect"; } else { elem.innerhtml = ""; } return response.blob(); }).then(function(imageblob) { let imgobjecturl = url.createobjecturl(imageblob); document.getelementbyid("img-element-id").src = imgobjecturl; }); disallowing redirects because using redirected to manually filter out redirects ca...
...n allow forgery of redirects, you should instead set the redirect mode to "error" in the init parameter when calling fetch(), like this: fetch("awesome-picture.jpg", { redirect: "error" }).then(function(response) { return response.blob(); }).then(function(imageblob) { let imgobjecturl = url.createobjecturl(imageblob); document.getelementbyid("img-element-id").src = imgobjecturl; }); specifications specification status comment fetchthe definition of 'redirected' in that specification.

Storage - Web APIs
if(!localstorage.getitem('bgcolor')) { populatestorage(); } setstyles(); function populatestorage() { localstorage.setitem('bgcolor', document.getelementbyid('bgcolor').value); localstorage.setitem('font', document.getelementbyid('font').value); localstorage.setitem('image', document.getelementbyid('image').value); } function setstyles() { var currentcolor = localstorage.getitem('bgcolor'); var currentfont = localstorage.getitem('font'); var currentimage = localstorage.getitem('image'); document.getelementbyid('bgcolor').value = currentc...
...olor; document.getelementbyid('font').value = currentfont; document.getelementbyid('image').value = currentimage; htmlelem.style.backgroundcolor = '#' + currentcolor; pelem.style.fontfamily = currentfont; imgelem.setattribute('src', currentimage); } note: to see this running as a complete working example, see our web storage demo.

TextMetrics - Web APIs
html <canvas id="canvas" width="550" height="500"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const baselinesabovealphabetic = ['fontboundingboxascent', 'actualboundingboxascent', 'emheightascent', 'hangingbaseline']; const baselinesbelowalphabetic = ['ideographicbaseline', 'emheightdescent', 'actualboundingboxdescent', 'fontboundingboxdescent']; const baselines = [...baselinesabovealphabetic, ...baseli...
... it can therefore be useful to use the sum of actualboundingboxleft and actualboundingboxright as a more accurate way to get the absolute text width: const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const text = 'abcdefghijklmnop'; ctx.font = 'italic 50px serif'; const textmetrics = ctx.measuretext(text); console.log(textmetrics.width); // 459.8833312988281 console.log(math.abs(textmetrics.actualboundingboxleft) + math.abs(textmetrics.actualboundingboxright)); // 462.8833333333333 specifications specification ...

VisualViewport - Web APIs
var bottombar = document.getelementbyid('bottombar'); var viewport = window.visualviewport; function resizehandler() { if (viewport.scale > 1.3) bottombar.style.display = "none"; else bottombar.style.display = "block"; } window.visualviewport.addeventlistener('resize', resizehandler); simulating position: device-fixed this example, also taken from the visual viewport readme, shows how to use this api to simulate pos...
... var bottombar = document.getelementbyid('bottombar'); var viewport = window.visualviewport; function viewporthandler() { var layoutviewport = document.getelementbyid('layoutviewport'); // since the bar is position: fixed we need to offset it by the visual // viewport's offset from the layout viewport origin.

A basic 2D WebGL animation example - Web APIs
let uscalingfactor; let uglobalcolor; let urotationvector; let avertexposition; // animation timing let previoustime = 0.0; let degreespersecond = 90.0; initializing the program is handled through a load event handler called startup(): window.addeventlistener("load", startup, false); function startup() { glcanvas = document.getelementbyid("glcanvas"); gl = glcanvas.getcontext("webgl"); const shaderset = [ { type: gl.vertex_shader, id: "vertex-shader" }, { type: gl.fragment_shader, id: "fragment-shader" } ]; shaderprogram = buildshaderprogram(shaderset); aspectratio = glcanvas.width/glcanvas.height; currentrotation = [0, 1]; currentscale = [1.0, aspectratio]; vertexarray =...
... function compileshader(id, type) { let code = document.getelementbyid(id).firstchild.nodevalue; let shader = gl.createshader(type); gl.shadersource(shader, code); gl.compileshader(shader); if (!gl.getshaderparameter(shader, gl.compile_status)) { console.log(`error compiling ${type === gl.vertex_shader ?

Using the Web Storage API - Web APIs
for example: function setstyles() { var currentcolor = localstorage.getitem('bgcolor'); var currentfont = localstorage.getitem('font'); var currentimage = localstorage.getitem('image'); document.getelementbyid('bgcolor').value = currentcolor; document.getelementbyid('font').value = currentfont; document.getelementbyid('image').value = currentimage; htmlelem.style.backgroundcolor = '#' + currentcolor; pelem.style.fontfamily = currentfont; imgelem.setattribute('src', currentimage); } here, the first three lines grab the values from local storage.
... function populatestorage() { localstorage.setitem('bgcolor', document.getelementbyid('bgcolor').value); localstorage.setitem('font', document.getelementbyid('font').value); localstorage.setitem('image', document.getelementbyid('image').value); setstyles(); } the populatestorage() function sets three items in local storage — the background color, font, and image path.

Using Web Workers - Web APIs
{ listeners[event.data.querymethodlistener].apply(instance, event.data.querymethodarguments); } else { this.defaultlistener.call(instance, event.data); } } } // your custom "queryable" worker var mytask = new queryableworker('my_task.js'); // your custom "listeners" mytask.addlistener('printstuff', function (result) { document.getelementbyid('firstlink').parentnode.appendchild(document.createtextnode('the difference is ' + result + '!')); }); mytask.addlistener('doalert', function (time, unit) { alert('worker waited for ' + time + ' ' + unit + ' :-)'); }); </script> </head> <body> <ul> <li><a id="firstlink" href="javascript:mytask.sendquery('getdifference', 5, 3);">what is the difference between 5 and 3?</a><...
... the html code <!doctype html> <html> <head> <meta charset="utf-8" /> <title>test threads fibonacci</title> </head> <body> <div id="result"></div> <script language="javascript"> var worker = new worker('fibonacci.js'); worker.onmessage = function(event) { document.getelementbyid('result').textcontent = event.data; dump('got: ' + event.data + '\n'); }; worker.onerror = function(error) { dump('worker error: ' + error.message + '\n'); throw error; }; worker.postmessage('5'); </script> </body> </html> the web page creates a div element with the id result , which gets used to display the result, then spawns the worker.

Window.getDefaultComputedStyle() - Web APIs
example simple example var elem1 = document.getelementbyid("elemid"); var style = window.getdefaultcomputedstyle(elem1); longer example <style> #elem-container { position: absolute; left: 100px; top: 200px; height: 100px; } </style> <div id="elem-container">dummy</div> <div id="output"></div> <script> var elem = document.getelementbyid("elem-container"); var thecssprop = window.getdefaultcomputedstyle(elem).position; documen...
...t.getelementbyid("output").innerhtml = thecssprop; // will output "static" </script> use with pseudo-elements the getdefaultcomputedstyle() method can pull style info from pseudo-elements (e.g., ::before or ::after).

WindowOrWorkerGlobalScope.setInterval() - Web APIs
<!doctype html> <html> <head> <meta charset="utf-8" /> <title>setinterval/clearinterval example</title> <script> var nintervid; function changecolor() { nintervid = setinterval(flashtext, 1000); } function flashtext() { var oelem = document.getelementbyid('my_box'); oelem.style.color = oelem.style.color == 'red' ?
...'hidden' : 'visible'; } } var fadeinout = new minidaemon(document.getelementbyid('sample_div'), opacity, 300, 8); </script> </body> </html> view this example in action usage notes the setinterval() function is commonly used to set a delay for functions that are executed again and again, such as animations.

ARIA live regions - Accessibility
<div id="clock" role="timer" aria-live="polite"></div> /* basic javascript to update the clock */ setinterval(function() { var now = new date(); document.getelementbyid('clock').innerhtml = "time: " + now.gethours() + ":" + ("0"+now.getminutes()).substr(-2); }, 60000); the first time the function executes, the entirety of the string that is added will be announced.
... a working example of a simple year control for better understanding: <div id="date-input"> <label>year: <input type="text" id="year" value="1990" onblur="change(event)"/> </label> </div> <div id="date-output" aria-live="polite"> the set year is: <span id="year-output">1990</span> </div> function change(event) { var yearout = document.getelementbyid("year-output"); switch (event.target.id) { case "year": yearout.innerhtml = event.target.value; break; default: return; } }; without aria-atomic="true" the screenreader announces only the changed value of year.

Using the alert role - Accessibility
the pseudo code snippet below illustrates this approach: <p id="forminstruction">you must select at least 3 options</p> // when the user tries to submit the form with less than 3 checkboxes selected: document.getelementbyid("forminstruction").setattribute("role", "alert"); example 4: making an element with an alert role visible if an element already has role="alert" and is initially hidden using css, making it visible will cause the alert to fire as if it was just added to the page.
... .hidden { display:none; } <p id="expirationwarning" role="alert" class="hidden">your log in session will expire in 2 minutes</p> // removing the 'hidden' class makes the element visible, which will make the screen reader announce the alert: document.getelementbyid("expirationwarning").classname = ""; working examples: alert role example using an aria alert box alert example using a modal aria dialog box notes using the alert role on an element implies that element has aria-live="assertive".

Using the aria-invalid attribute - Accessibility
the snippet below shows a very simple validation function, which only checks for the presence of a particular character (in the real world, validation will likely be more sophisticated): function checkvalidity(aid, asearchterm, amsg){ var elem = document.getelementbyid(aid); var invalid = (elem.value.indexof(asearchterm) < 0); if (invalid) { elem.setattribute("aria-invalid", "true"); updatealert(amsg); } else { elem.setattribute("aria-invalid", "false"); updatealert(); } } the snippet below shows the alert functions, which add (or remove) the error message: function updatealert(msg) { var oldalert = documen...
...t.getelementbyid("alert"); if (oldalert) { document.body.removechild(oldalert); } if (msg) { var newalert = document.createelement("div"); newalert.setattribute("role", "alert"); newalert.setattribute("id", "alert"); var content = document.createtextnode(msg); newalert.appendchild(content); document.body.appendchild(newalert); } } note that the alert has the aria role attribute set to "alert." working examples: alert role example (uses the aria-invalid attribute) notes when aria-invalid is used in conjunction with the aria-required attribute, aria-invalid should not be set to true before the form is submitted - only in response to validation.

Alerts - Accessibility
below is example javascript code which could be inserted above the closing “head” tag: <script type="application/javascript"> function removeoldalert() { var oldalert = document.getelementbyid("alert"); if (oldalert){ document.body.removechild(oldalert); } } function addalert(amsg) { removeoldalert(); var newalert = document.createelement("div"); newalert.setattribute("role", "alert"); newalert.setattribute("id", "alert"); var msg = document.createtextnode(amsg); newalert.appendchild(msg); document.body.appendchild(newalert); } function checkvalid...
...ity(aid, asearchterm, amsg) { var elem = document.getelementbyid(aid); var invalid = (elem.value.indexof(asearchterm) < 0); if (invalid) { elem.setattribute("aria-invalid", "true"); addalert(amsg); } else { elem.setattribute("aria-invalid", "false"); removeoldalert(); } } </script> the checkvalidity function the primary method in javascript used for form validation is the checkvalidity function.

:scope - CSS: Cascading Style Sheets
javascript let paragraph = document.getelementbyid("para"); let output = document.getelementbyid("output"); if (paragraph.matches(":scope")) { output.innertext = "yep, the element is its own scope as expected!"; } html <p id="para"> this is a paragraph.
... javascript var context = document.getelementbyid('context'); var selected = context.queryselectorall(':scope > div'); document.getelementbyid('results').innerhtml = array.prototype.map.call(selected, function (element) { return '#' + element.getattribute('id'); }).join(', '); html <div id="context"> <div id="element-1"> <div id="element-1.1"></div> <div id="element-1.2"></div> </div> <div id="element-2"> <div id="element-2.1"></div> </div> </div> <p> selected elements ids : <span id="results"></span> </p> r...

Using CSS animations - CSS: Cascading Style Sheets
var element = document.getelementbyid("watchme"); element.addeventlistener("animationstart", listener, false); element.addeventlistener("animationend", listener, false); element.addeventlistener("animationiteration", listener, false); element.classname = "slidein"; this is pretty standard code; you can get details on how it works in the documentation for eventtarget.addeventlistener().
... l = document.createelement("li"); switch(event.type) { case "animationstart": l.innerhtml = "started: elapsed time is " + event.elapsedtime; break; case "animationend": l.innerhtml = "ended: elapsed time is " + event.elapsedtime; break; case "animationiteration": l.innerhtml = "new loop started at time " + event.elapsedtime; break; } document.getelementbyid("output").appendchild(l); } this code, too, is very simple.

Border-radius generator - CSS: Cascading Style Sheets
ueryselectorall('.ui-checkbox'); var size = elem.length; for (var i = 0; i < size; i++) new checkbox(elem[i]); } return { init : init, setvalue : setvalue, subscribe : subscribe, unsubscribe : unsubscribe } })(); window.addeventlistener("load", function() { borderradius.init(); }); var borderradius = (function borderradius() { function getelembyid(id) { return document.getelementbyid(id); } /** * shadow dragging */ var previewmousetracking = (function drag() { var active = false; var lastx = 0; var lasty = 0; var subscribers = []; var init = function init(id) { var elem = getelembyid(id); elem.addeventlistener('mousedown', dragstart, false); document.addeventlistener('mouseup', dragend, false); } var dragstart = function dragstart(e) { if (...
...etnode(this.topic); this.setunitx(this.unitx); this.setunity(this.unity); this.setunitr(this.unitr); this.updatewidth(); this.updateheight(); this.updateradius(); if (x === 'left') this.resizex = 1; if (x === 'right') this.resizex = -1; if (y === 'top') this.resizey = 1; if (y === 'bottom') this.resizey = -1; radius.classname = 'radius'; var unit_selector = document.getelementbyid("unit-selection"); var unitw = new unitselector(this.topic + '-w'); var unith = new unitselector(this.topic + '-h'); var unitr = new unitselector(this.topic); unit_selector.appendchild(unitw.container); unit_selector.appendchild(unith.container); unit_selector.appendchild(unitr.container); node.appendchild(radius); subject.appendchild(handle); unitw.select.addeventlistener('ch...

Color picker tool - CSS: Cascading Style Sheets
y: 0; top: -10000px; left: 0; color: #777; float: left; transition: opacity 1s; } #zindex input { border: 1px solid #ddd; font-size: 16px; color: #777; } #zindex .ui-input-slider-info { width: 60px; } #zindex[data-active='true'] { top: 0; opacity: 1; } javascript content 'use strict'; var uicolorpicker = (function uicolorpicker() { function getelembyid(id) { return document.getelementbyid(id); } var subscribers = []; var pickers = []; /** * rgba color class * * hsv/hsb and hsl (hue, saturation, value / brightness, lightness) * @param hue 0-360 * @param saturation 0-100 * @param value 0-100 * @param lightness 0-100 */ function color(color) { if(color instanceof color === true) { this.copy(color); return; } this.r = 0; this.g = 0; this.
...ubscribe : unsubscribe, setprecision : setprecision, setsensivity : setsensivity, getprecision : getprecision, createslider : createslider, }; })(); 'use strict'; window.addeventlistener("load", function() { colorpickertool.init(); }); var colorpickertool = (function colorpickertool() { /*========== get dom element by id ==========*/ function getelembyid(id) { return document.getelementbyid(id); } function allowdropevent(e) { e.preventdefault(); } /*========== make an element resizable relative to it's parent ==========*/ var uicomponent = (function uicomponent() { function makeresizable(elem, axis) { var valuex = 0; var valuey = 0; var action = 0; var resizestart = function resizestart(e) { e.stoppropagation(); e.preventdefault(); if (e.button ...

Linear-gradient Generator - CSS: Cascading Style Sheets
px 5%; color: #777; position: relative; float: left; } #output .property { height: 100%; width: 12%; position: absolute; left: 0; } #output .value { width: 88%; position: absolute; white-space: pre; word-wrap: break-word; display: block; right: 0; } javascript content var uicolorpicker = (function uicolorpicker() { 'use strict'; function getelembyid(id) { return document.getelementbyid(id); } var subscribers = []; var pickers = []; /** * rgba color class * * hsv/hsb and hsl (hue, saturation, value / brightness, lightness) * @param hue 0-360 * @param saturation 0-100 * @param value 0-100 * @param lightness 0-100 */ function color(color) { if(color instanceof color === true) { this.copy(color); return; } this.r = 0; this.g = 0; this.
...entlistener("load", function() { lineargradienttool.init(); }); window.addeventlistener("load", function() { lineargradienttool.init(); }); var lineargradienttool = (function lineargradienttool() { 'use strict'; var radian = 180 / math.pi; var inv_radian = math.pi / 180; var units = {'%': 1, 'px' : 0}; /*========== dom methods ==========*/ function getelembyid(id) { return document.getelementbyid(id); } function allowdropevent(e) { e.preventdefault(); } function createclasselement(tag, classname, parent) { var elem = document.createelement(tag); elem.classname = classname; if (parent) parent.appendchild(elem); return elem; }; function trackmouse(elem, callback, startfunc, endfunc) { startfunc = startfunc || function(e) {}; endfunc = endfunc || function(e) {}; ele...

place-content - CSS: Cascading Style Sheets
ter</option> <option value="start">start</option> <option value="end">end</option> <option value="flex-start">flex-start</option> <option value="flex-end">flex-end</option> <option value="left">left</option> <option value="right">right</option> <option value="safe">safe</option> <option value="unsafe">unsafe</option> </select><code>;</code> var update = function () { document.getelementbyid("container").style.placecontent = document.getelementbyid("aligncontentalignment").value + " " + document.getelementbyid("justifycontentalignment").value; } var aligncontentalignment = document.getelementbyid("aligncontentalignment"); aligncontentalignment.addeventlistener("change", update); var justifycontentalignment = document.getelementbyid("justifycontentalignment"); justifycontentalignme...
...nt.addeventlistener("change", update); var writingm = document.getelementbyid("writingmode"); writingm.addeventlistener("change", function (evt) { document.getelementbyid("container").style.writingmode = evt.target.value; }); var direction = document.getelementbyid("direction"); direction.addeventlistener("change", function (evt) { document.getelementbyid("container").style.direction = evt.target.value; }); css #container { display: flex; height:240px; width: 240px; flex-wrap: wrap; background-color: #8c8c8c; writing-mode: horizontal-tb; /* can be changed in the live sample */ direction: ltr; /* can be changed in the live sample */ place-content: flex-end center; /* can be changed in the live sample */ } div > div { border: 2px solid #8c8c8c; width: 50px; background-col...

Creating a cross-browser video player - Developer guides
a number of variables pointing to html elements are required: var videocontainer = document.getelementbyid('videocontainer'); var video = document.getelementbyid('video'); var videocontrols = document.getelementbyid('video-controls'); as mentioned earlier, the browser's default controls now need to be disabled, and the custom controls need to be displayed: // hide the default controls video.controls = false; // display the user defined video controls videocontrols.style.display = 'block'; with t...
...hat done, a variable pointing to each of the buttons is now required: var playpause = document.getelementbyid('playpause'); var stop = document.getelementbyid('stop'); var mute = document.getelementbyid('mute'); var volinc = document.getelementbyid('volinc'); var voldec = document.getelementbyid('voldec'); var progress = document.getelementbyid('progress'); var progressbar = document.getelementbyid('progress-bar'); var fullscreen = document.getelementbyid('fs'); using these handles, events can now be attached to each of the custom control buttons making them interactive.

Audio and Video Delivery - Developer guides
to grab the stream from your webcam, first set up a <video> element: <video id="webcam" width="480" height="360"></video> next, if supported connect the webcam source to the video element: if (navigator.mediadevices) { navigator.mediadevices.getusermedia({ video: true, audio: false }) .then(function onsuccess(stream) { var video = document.getelementbyid('webcam'); video.autoplay = true; video.srcobject = stream; }) .catch(function onerror() { alert('there has been a problem retreiving the streams - are you running on file:/// or did you disallow access?'); }); } else { alert('getusermedia is not supported in this browser.'); } to find out more, read our mediadevices.getusermedia page.
... a quick example — first set up your audio and custom controls in html: <audio id="my-audio" src="http://jplayer.org/audio/mp3/miaow-01-tempered-song.mp3"></audio> <button id="my-control">play</button> add a bit of javascript to detect events to play and pause the audio: window.onload = function() { var myaudio = document.getelementbyid('my-audio'); var mycontrol = document.getelementbyid('my-control'); function switchstate() { if (myaudio.paused == true) { myaudio.play(); mycontrol.innerhtml = "pause"; } else { myaudio.pause(); mycontrol.innerhtml = "play"; } } function checkkey(e) { if (e.keycode == 32 ) { //spacebar switchstate(); } } mycontrol.addeventlistener(...

Using device orientation with 3D transforms - Developer guides
here's a simple code snippet to sum it up: var elem = document.getelementbyid("view3d"); window.addeventlistener("deviceorientation", function(e) { // remember to use vendor-prefixed transform property elem.style.transform = "rotatez(" + ( e.alpha - 180 ) + "deg) " + "rotatex(" + e.beta + "deg) " + "rotatey(" + ( -e.gamma ) + "deg)"; }); orientation compensation compensating the orientation of the device can be useful to create parallax effects or augme...
...this is achieved by inverting the previous order of rotations and negating the alpha value: var elem = document.getelementbyid("view3d"); window.addeventlistener("deviceorientation", function(e) { // again, use vendor-prefixed transform property elem.style.transform = "rotatey(" + ( -e.gamma ) + "deg)" + "rotatex(" + e.beta + "deg) " + "rotatez(" + - ( e.alpha - 180 ) + "deg) "; }); rotate3d to orientation should you ever need to convert a rotate3d axis-angle to orientation euler angles, you can use the following algorithm: // convert a rotate3d axis-angle to deviceorientation angles function orient( aa ) { var x = aa.x, y = aa.y, z = aa.z, a = aa.a, c = math.cos( aa.a ), s = math.sin( aa.a ), t = 1 - c, // axis-angle to rotation ma...

Rich-Text Editing in Mozilla - Developer guides
figure 3 : setting up rich-text editing html: <body onload="load()"> javascript: function load(){ getiframedocument("editorwindow").designmode = "on"; } function getiframedocument(aid){ // if contentdocument exists, w3c compliant (mozilla) if (document.getelementbyid(aid).contentdocument){ return document.getelementbyid(aid).contentdocument; } else { // ie return document.frames[aid].document; } } the example contains a doricheditcommand function that makes it easier to execute commands on the iframe's document and keeps the html code clean.
... figure 4 : executing rich editing commands html: <button onclick="doricheditcommand('bold')" style="font-weight:bold;">b</button> javascript: function doricheditcommand(aname, aarg){ getiframedocument('editorwindow').execcommand(aname,false, aarg); document.getelementbyid('editorwindow').contentwindow.focus() } example: a simple but complete rich text editor <!doctype html> <html> <head> <title>rich text editor</title> <script type="text/javascript"> var odoc, sdeftxt; function initdoc() { odoc = document.getelementbyid("textbox"); sdeftxt = odoc.innerhtml; if (document.compform.switchmode.checked) { setdocmode(true); } } function formatdoc(scmd, svalu...

<input type="password"> - HTML: Hypertext Markup Language
html <label for="userpassword">password: </label> <input id="userpassword" type="password" size="12"> <button id="selectall">select all</button> javascript document.getelementbyid("selectall").onclick = function() { document.getelementbyid("userpassword").select(); } result you can also use selectionstart and selectionend to get (or set) what range of characters in the control are currently selected, and selectiondirection to know which direction selection occurred in (or will be extended in, depending on your platform; see its documentation for an explanation).
... var ssn = document.getelementbyid("ssn"); var current = document.getelementbyid("current"); ssn.oninput = function(event) { current.innerhtml = ssn.value; } result specifications specification status comment html living standardthe definition of '<input type="password">' in that specification.

Promise - JavaScript
"use strict"; var promisecount = 0; function testpromise() { let thispromisecount = ++promisecount; let log = document.getelementbyid('log'); // begin log.insertadjacenthtml('beforeend', thispromisecount + ') started (sync code started)'); // we make a new promise: we promise a numeric count of this promise, starting from 1 (after waiting 3s) let p1 = new promise((resolve, reject) => { // the executor function is called with the ability to resolve or reject the promise log.insertadjacenthtml('beforeend', thispro...
... fulfillment value log.insertadjacenthtml('beforeend', val + ') promise fulfilled (async code terminated)'); }).catch((reason) => { // log the rejection reason console.log(`handle rejected promise (${reason}) here.`); }); // end log.insertadjacenthtml('beforeend', thispromisecount + ') promise made (sync code terminated)'); } if ("promise" in window) { let btn = document.getelementbyid("btn"); btn.addeventlistener("click",testpromise); } else { log = document.getelementbyid('log'); log.innerhtml = "live example not available as your browser doesn't support the <code>promise<code> interface."; } this example is started by clicking the button.

How to make PWAs re-engageable using Notifications and Push - Progressive web apps (PWAs)
instead of showing the notification immediately though, best practice dictates that we should show the popup when the user requests it by clicking on a button: var button = document.getelementbyid("notifications"); button.addeventlistener('click', function(e) { notification.requestpermission().then(function(result) { if(result === 'granted') { randomnotification(); } }); }); this shows a popup using the operating system’s own notifications service: when the user confirms to receive notifications, the app can then show them.
... fetch('./register', { method: 'post', headers: { 'content-type': 'application/json' }, body: json.stringify({ subscription: subscription }), }); then the globaleventhandlers.onclick function on the subscribe button is defined: document.getelementbyid('doit').onclick = function() { const payload = document.getelementbyid('notification-payload').value; const delay = document.getelementbyid('notification-delay').value; const ttl = document.getelementbyid('notification-ttl').value; fetch('./sendnotification', { method: 'post', headers: { 'content-type': 'application/json' }, body: json.

Structural overview of progressive web apps - Progressive web apps (PWAs)
var entry = template.replace(/pos/g,(i+1)) .replace(/slug/g,games[i].slug) .replace(/name/g,games[i].name) .replace(/author/g,games[i].author) .replace(/twitter/g,games[i].twitter) .replace(/website/g,games[i].website) .replace(/github/g,games[i].github); entry = entry.replace('<a href=\'http:///\'></a>','-'); content += entry; }; document.getelementbyid('content').innerhtml = content; then it registers a service worker: if ("serviceworker" in navigator) { navigator.serviceworker.register("/pwa-examples/js13kpwa/sw.js"); } after that, the app adds a handler for clicks on a button whose id is notifications; this handler requests permission to send notifications to the user, then generates and sends a random notification.
... var button = document.getelementbyid("notifications"); button.addeventlistener('click', function(e) { notification.requestpermission().then(function(result) { if (result === 'granted') { randomnotification(); } }); }); the randomnotification() function follows, rounding out the last of the code in the file: function randomnotification() { var randomitem = math.floor(math.random()*games.length); var notiftitle = games[randomitem].name; var notifbody = 'created by '+games[randomitem].author+'.'; var notifimg = 'data/img/'+games[randomitem].slug+'.jpg'; var options = { body: notifbody, icon: notifimg } var notif = new notification(notiftitle, options); settimeout(randomnotification, 30000); } the service worker the last file we'll briefly look at here is ...

Scripting - SVG: Scalable Vector Graphics
the best way to get access to the document representing an svg document is to look at htmliframeelement.contentdocument (if the document is presented in an <iframe>) or htmlobjectelement.contentdocument (if the document is presented in an <object> element), like this: var svgdoc = document.getelementbyid("iframe_element").contentdocument; in addition, the <iframe>, <embed>, and <object> elements offer a method, getsvgdocument(), which returns the xmldocument representing the element's embedded svg or null if the element doesn't represent an svg document.
... you can also use document.getelementbyid("svg_elem_name").getsvgdocument(), which gives the same result.

Advanced Example - XSLT: Extensible Stylesheet Language Transformations
// importnode is used to clone the nodes we want to process via xslt - true makes it do a deep clone var mynode = document.getelementbyid("example"); var clonednode = xmlref.importnode(mynode, true); // after cloning, we append xmlref.appendchild(clonednode); // set the sorting parameter in the xsl file var sortval = xsltprocessor.getparameter(null, "myorder"); if (sortval == "" || sortval == "descending") xsltprocessor.setparameter(null, "myorder", "ascending"); else xsltprocessor.setparameter(null, "myord...
...er", "descending"); // initiate the transformation var fragment = xsltprocessor.transformtofragment(xmlref, document); // clear the contents document.getelementbyid("example").innerhtml = ""; mydom = fragment; // add the new content from the transformation document.getelementbyid("example").appendchild(fragment) } // xsl stylesheet: <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns="http://www.w3.org/1999/xhtml" xmlns:html="http://www.w3.org/1999/xhtml" xmlns:xsl="http://www.w3.org/1999/xsl/transform"> <xsl:output method="html" indent="yes" /> <xsl:param name="myorder" /> <xsl:template match="/"> <xsl:apply-templates select="/div//div"> <xsl:sort select="." data-type="number" order="{$myorder}" /> </xsl:apply-templates> </xsl:template>...

XUL Migration Guide - Archive of obsolete content
here's a really simple example add-on that modifies the browser chrome using window/utils: function removeforwardbutton() { var window = require("sdk/window/utils").getmostrecentbrowserwindow(); var forward = window.document.getelementbyid('forward-button'); var parent = window.document.getelementbyid('urlbar-container'); parent.removechild(forward); } require("sdk/ui/button/action").actionbutton({ id: "remove-forward-button", label: "remove forward button", icon: "./icon-16.png", onclick: removeforwardbutton }); there are more useful examples of this technique in the jetpack wiki's collection of third party modules.

Creating annotations - Archive of obsolete content
here's the code: var textarea = document.getelementbyid('annotation-box'); textarea.onkeyup = function(event) { if (event.keycode == 13) { self.postmessage(textarea.value); textarea.value = ''; } }; self.on('message', function() { var textarea = document.getelementbyid('annotation-box'); textarea.value = ''; textarea.focus(); }); save this inside data/editor as annotation-editor.js.

Display a Popup - Archive of obsolete content
var textarea = document.getelementbyid("edit-box"); textarea.addeventlistener('keyup', function onkeyup(event) { if (event.keycode == 13) { // remove the newline.

Downloading Files - Archive of obsolete content
var privacy = privatebrowsingutils.privacycontextfromwindow(aurlsourcewindow); var progresselement = document.getelementbyid("progress_element"); persist.progresslistener = { onprogresschange: function(awebprogress, arequest, acurselfprogress, amaxselfprogress, acurtotalprogress, amaxtotalprogress) { var percentcomplete = math.round((acurtotalprogress / amaxtotalprogress) * 100); progresselement.textcontent = percentcomplete +"%"; }, onstatechange: function(awebprogress, arequest, astateflags, astatus) { ...

On page load - Archive of obsolete content
ript to your overlay (see "attaching a script to an overlay") that adds a load event listener to appcontent element (browsers) or messagepane (mail): window.addeventlistener("load", function load(event){ window.removeeventlistener("load", load, false); //remove listener, no longer needed myextension.init(); },false); var myextension = { init: function() { var appcontent = document.getelementbyid("appcontent"); // browser if(appcontent){ appcontent.addeventlistener("domcontentloaded", myextension.onpageload, true); } var messagepane = document.getelementbyid("messagepane"); // mail if(messagepane){ messagepane.addeventlistener("load", function(event) { myextension.onpageload(event); }, true); } }, onpageload: function(aevent) { var doc = aevent.o...

Tabbox - Archive of obsolete content
handling onclosetab event assuming the tabbox, tabs, and tabpanels widgets with id's the same as their nodename, this function will correctly remove the current tab and tab panel for the onclosetab tabs event: function removetab(){ var tabbox = document.getelementbyid("tabbox"); var currentindex = tabbox.selectedindex; if(currentindex>=0){ var tabs=document.getelementbyid("tabs"); var tabpanels=document.getelementbyid("tabpanels"); tabpanels.removechild(tabpanels.childnodes[currentindex]); tabs.removeitemat(currentindex); /*work around if last tab is removed, widget fails to advance to next tab*/ if(-1 == tabbox.selectedindex &&...

Toolbar - Archive of obsolete content
@optional */ function installbutton(toolbarid, id, afterid) { if (!document.getelementbyid(id)) { var toolbar = document.getelementbyid(toolbarid); // if no afterid is given, then append the item to the toolbar var before = null; if (afterid) { let elem = document.getelementbyid(afterid); if (elem && elem.parentnode == toolbar) before = elem.nextelementsibling; } toolbar.insertitem(id, before); ...

Windows - Archive of obsolete content
var hr = document.createelementns("http://www.w3.org/1999/xhtml", "html:hr"); document.getelementbyid("id1").appendchild(hr); ...

Displaying web content in an extension without security issues - Archive of obsolete content
for example, your template document might have this code: <style type="text/css"> #entrytemplate { display: none; } </style> <div id="entrytemplate"> <div class="title"></div> <div class="description"></div> </div> now to insert a new entry in the document you would do the following: var template = doc.getelementbyid("entrytemplate"); var entry = template.clonenode(true); entry.removeattribute("id"); entry.getelementsbyclassname("title")[0].textcontent = title; entry.getelementsbyclassname("description")[0].textcontent = description; template.parentnode.appendchild(entry); the important difference here is that the result will always have the same structure as the template tag.

How to convert an overlay extension to restartless - Archive of obsolete content
docs: document.getelementbyid(), document.createelement(), element reference, node reference (dom elements are also nodes).

Inline options - Archive of obsolete content
for example: var observer = { observe: function(asubject, atopic, adata) { if (atopic == "addon-options-displayed" && adata == "my_addon@my_domain") { var doc = asubject; var control = doc.getelementbyid("myaddon-pref-control"); control.value = "test"; } } }; services.obs.addobserver(observer, "addon-options-displayed", false); // don't forget to remove your observer when your add-on is shut down.

Interaction between privileged and non-privileged pages - Archive of obsolete content
var targetdoc = null; function onload() { var iframe = document.getelementbyid("contentiframe"); targetdoc = iframe.contentdocument; iframe.contentwindow.addeventlistener("newstuff", receivestufffrompage, false); } function receivestufffrompage(event) { var uc = geteventdata(event); // uc = unchecked data in form of e4x xml var stuff = {}; stuff.id = sanitize.integer(uc.@id); stuff.name = sanitize.label(uc.@name); } function sendsomethingtopage (something) { ...

Chapter 3: Introduction to XUL—How to build a more intuitive UI - Archive of obsolete content
var item = document.getelementbyid('menu-item-custom'); function handlecommandevent(aevent) { alert('ok'); item.removeeventlistener('command', handlecommandevent, false); item.parentnode.removechild(item); } item.addeventlistener('command', handlecommandevent, false); listing 11: additions and deletions using a dynamic event listener special menu items much like input elements in html, menuitem elements can operate like...

Chapter 5: Let's build a Firefox extension - Archive of obsolete content
load="initclock();"> <script type="application/javascript" src="chrome://helloworld/content/clock.js"/> <hbox align="center"> <label value="current time:" /> <textbox id="currenttime" /> </hbox> </dialog> listing 6: content for clock.js function initclock() { showcurrenttime(); window.setinterval(showcurrenttime, 1000); } function showcurrenttime() { var textbox = document.getelementbyid("currenttime"); textbox.value = new date().tolocaletimestring(); textbox.select(); } operations check perform an operations check to make sure that your changes to the source file are correct.

Chapter 2: Technologies used in developing extensions - Archive of obsolete content
listing 4: an example manipulation using the dom var bar = document.getelementbyid('toolbar'); bar.removechild(bar.childnodes[1]); bar.appendchild(document.createelement('button')); bar.lastchild.setattribute('label', 'hello!'); « previousnext » ...

Chapter 4: Using XPCOM—Implementing advanced processes - Archive of obsolete content
listing 21: loading a page by setting a referrer var browser = document.getelementbyid('browser'); var ioservice = components.classes['@mozilla.org/network/io-service;1'] .getservice(components.interfaces.nsiioservice); var referrer = ioservice.newuri('http://www.gihyo.co.jp/', null, null); browser.loaduri('http://www.gihyo.co.jp/magazines/sd', referrer); listing 22: loading a page with data transmitted via the post method var content = encodeuricomponent('passwo...

Adding Events and Commands - Archive of obsolete content
let onlinebroadcaster = document.getelementbyid("xulschoolhello-online-broadcaster"); onlinebroadcaster.setattribute("label", "something"); you can also have finer-grained control to this behavior by adding the observes element as a child to your observer node.

Connecting to Remote Content - Archive of obsolete content
request.onload = function(aevent) { let responsexml = aevent.target.responsexml; let xulnode; // transform the xml document to a xul document xuldocument = xsltprocessor.transformtodocument(responsexml); // append the xul node to a xul element xulnode = document.adoptnode(xuldocument.firstchild); document.getelementbyid("foo").appendchild(xulnode); }; we effectively transformed the xml file into xul and integrated it into the ui.

Adding preferences to an extension - Archive of obsolete content
rmation: function() { // because we may be called as a callback, we can't rely on // "this" referring to the right object, so we need to reference // it by its full name var symbol = stockwatcher.tickersymbol; var fullurl = "http://quote.yahoo.com/d/quotes.csv?f=sl1d1t1c1ohgv&e=.csv&s=" + symbol; function inforeceived() { var samplepanel = document.getelementbyid('stockwatcher2'); var output = httprequest.responsetext; if (output.length) { // remove any whitespace from the end of the string output = output.replace(/\w*$/, ""); // build the tooltip string var fieldarray = output.split(","); samplepanel.label = symbol + ": " + fieldarray[1]; samplepanel.tooltiptext = "chg: " + fieldarray[...

XUL user interfaces - Archive of obsolete content
copy and paste the content from here, making sure that you scroll to get all of it: // xul demonstration var datebox, daybox, currentday, status; // elements // called by window onload function init() { datebox = document.getelementbyid("date-text") daybox = document.getelementbyid("day-box") status = document.getelementbyid("status") settoday(); } // called by clear button function cleardate() { datebox.value = "" refresh() } // called by today button function settoday() { var d = new date() datebox.value = (d.getmonth() + 1) + "/" + d.getdate() + "/" + d.getfullyear() refresh() } // called by d...

JXON - Archive of obsolete content
*/ /* element.prototype.appendjxon = function (oobjtree) { loadobjtree(document, this, oobjtree); return this; }; */ example imagine you want to populate the following htmlelement through json: <div id="form_container"></div> then, the following code: document.getelementbyid("form_container").appendjxon({ "form": { "script": { "@type": "text/javascript", "keyvalue": "\n function numbersonly (otocheckfield, okeyevent) {\n return okeyevent.charcode === 0 || /\\d/.test(string.fromcharcode(okeyevent.charcode));\n }\n" }, "input": [{ "@type": "hidden", "@name": "instid", "@value": 1234 }, { "@type": "hidden", ...

Creating a Web based tone generator - Archive of obsolete content
und selected } var k = 2* math.pi * frequency / samplerate; for (var i=0, size=sounddata.length; i<size; i++) { sounddata[i] = math.sin(k * currentsoundsample++); } } var audiodestination = new audiodatadestination(samplerate, requestsounddata); function start() { currentsoundsample = 0; frequency = parsefloat(document.getelementbyid("freq").value); } function stop() { frequency = 0; } </script> </body> </html> ...

Monitoring WiFi access points - Archive of obsolete content
<html> <head> <title>wifi monitor example</title> <script> var count = 0; function test() { } test.prototype = { onchange: function (accesspoints) { netscape.security.privilegemanager.enableprivilege('universalxpconnect'); var d = document.getelementbyid("d"); d.innerhtml = ""; for (var i=0; i<accesspoints.length; i++) { var a = accesspoints[i]; d.innerhtml += "<p>" + a.mac + " " + a.ssid + " " + a.signal + "</p>"; } var c = document.getelementbyid("c"); c.innerhtml = "<p>" + count++ + "</p>"; }, onerror: function (value) { alert("error: " +value); }, queryinterface: function(iid) { netsca...

Enabling the behavior - updating the status bar panel - Archive of obsolete content
function updatetinderboxstatus() { var icon = document.getelementbyid('tinderbox-status'); if (gxmlhttprequest.responsetext.match("ee0000")) icon.setattribute("status", "busted"); else if (gxmlhttprequest.responsetext.match("ffaa00")) icon.setattribute("status", "testfailed"); else if (gxmlhttprequest.responsetext.match("11dd11")) icon.setattribute("status", "success"); else icon.setattribute("status", ""); } updatetinderboxstatus() retrieves a reference to the statusbarpanel element then searches through the retrieved html document (stored in the responsetext property of the xmlhttprequest instance) for one of several color references.

Jetpack Snippets - Archive of obsolete content
0, true); }}); calling into a slidebar from the global jetpack scope jetpack.slidebar.append({ onready: function (slide) { // call out to a global function, passing the slidebar object exinitslidebar(slide); }, ...});function exinitslidebar(aslidebar) { // this variable will now be global slider = aslidebar;} // then, accessing the slidebar htmlvar tl = slider.contentdocument.getelementbyid("thumblist"); // or calling slidebar api methods or accessing propertiesslider.notify(); ...

Anonymous Content - Archive of obsolete content
methods invoked on the document (e.g., getelementbyid) only see nodes that are at the document-level scope.

Binding Attachment and Detachment - Archive of obsolete content
var checkbox = document.getelementbyid("mycheckbox"); checkbox.style.mozbinding = "url(http://www.mozilla.org/xbl/htmlbindings.xml#checkbox)"; this attachment is not necessarily synchronous.

disabled - Archive of obsolete content
// disabling an element document.getelementbyid('buttonremove').setattribute("disabled", "disabled"); // enabling back an element by removing the "disabled" attribute document.getelementbyid('buttonremove').removeattribute("disabled"); firefox 3.5 note for keyset elements, support for this attribute was added in firefox 3.5.

oninput - Archive of obsolete content
--> <script language="javascript"> function setlabel(txtbox){ document.getelementbyid('lbl').value = txtbox.value; } </script> <label id="lbl"/> <textbox oninput="setlabel(this);"/> this is similar to the onkeypress event used in html documents.

statustext - Archive of obsolete content
tustext="connect to remote server" onmouseover="setstatusmessage(this)" onmouseout="clearstatusmessage()"/> <button label="ping" statustext="ping the server" onmouseover="setstatusmessage(this)" onmouseout="clearstatusmessage()"/> <statusbar> <statusbarpanel id="mystatuspanel" label="" flex="1"/> <spacer flex="1"/> </statusbar> <script> function setstatusmessage(obj){ document.getelementbyid('mystatuspanel').label = obj.getattribute('statustext'); } function clearstatusmessage(obj){ document.getelementbyid('mystatuspanel').label = ''; } </script> see also statusbar and statusbarpanel ...

appendItem - Archive of obsolete content
example <script language="javascript"> function additemstolist(){ var list = document.getelementbyid('mymenulist'); // add item with just the label list.appenditem('one'); // add item with label and value list.appenditem('two', 999); // select the first item list.selectedindex = 0; } </script> <button label="add items" oncommand="additemstolist()"/> <menulist id="mymenulist"> <menupopup/> </menulist> see also insertitemat() removeitemat() ...

insertItemAt - Archive of obsolete content
note: you cannot insert an item to an index that does not exist, eg: trying to insert an item at the end with element.getrowcount() + 1 example <!-- this example inserts at the selected item or appends, then selects the newly created item --> <script language="javascript"> function insertitemtolist(){ var mylistbox = document.getelementbyid('mylistbox'); // create a date to get some labels and values var somedate = new date(); if(mylistbox.selectedindex == -1){ // no item was selected in list so append to the end mylistbox.appenditem( somedate.tolocaletimestring(), somedate.gettime() ); var newindex = mylistbox.getrowcount() -1 }else{ // item was selected so insert at the selected i...

removeItemAt - Archive of obsolete content
<script language="javascript"> function removeselecteditem(){ var mylistbox = document.getelementbyid('mylistbox'); if(mylistbox.selectedindex == -1){ return; // no item selected so return }else{ mylistbox.removeitemat(mylistbox.selectedindex); } } function removeallitems(){ var mylistbox = document.getelementbyid('mylistbox'); var count = mylistbox.itemcount; while(count-- > 0){ mylistbox.removeitemat(0); } } </script> <button label="remove selected item" oncommand="removeselecteditem()"/> <button label="remove all items" oncommand="removeallitem...

Menus - Archive of obsolete content
for example, to have an item initially hidden in a window: function initmenus() { var item = document.getelementbyid("menu-file-open"); item.hidden = true; } the hidden property is set to true to hide the menu with the id 'menu-fileopen'.

Special per-platform menu considerations - Archive of obsolete content
for example, using document.getelementbyid() for the quit menu item returns the hidden item that still sits in the file menu.

controllers - Archive of obsolete content
example <window id="controller-example" title="controller example" onload="init();" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> function init() { var list = document.getelementbyid("thelist"); var listcontroller = { supportscommand : function(cmd){ return (cmd == "cmd_delete"); }, iscommandenabled : function(cmd){ if (cmd == "cmd_delete") return (list.selecteditem != null); return false; }, docommand : function(cmd){ list.removeitemat(list.selectedindex); }, onevent : function(evt){ } }; list.controllers.appendcontroller(lis...

currentIndex - Archive of obsolete content
<script language ="javascript"> function treerowclicked(){ var tree = document.getelementbyid("my-tree"); var selection = tree.view.selection; var celltext = tree.view.getcelltext(tree.currentindex, tree.columns.getcolumnat(0)); alert(celltext); } </script> <tree id="my-tree" seltype="single" onselect="treerowclicked()"> <treecols> <treecol label="title" flex="1"/><treecol label="url" flex="1"/> </treecols> <treechildren> <treeitem> <treerow> <tree...

disabled - Archive of obsolete content
<!-- checkbox enables/disables the button --> <checkbox label="enable button" oncommand="document.getelementbyid('buttremove').disabled = !

itemCount - Archive of obsolete content
example var bucket = document.getelementbyid("attachmentbucket"); if(bucket.itemcount == 0) { dump("\n\n no attachments \n\n"); } else { dump("\n\n attachment exists \n\n"); } ...

Actions - Archive of obsolete content
you can use getelementbyid to get at particular results, for instance document.getelementbyid("http://www.xulplanet.com/rdf/c") would retrieve the second generated button.

Simple Query Syntax - Archive of obsolete content
function applyfilter(country) { var rule = document.getelementbyid("filterrule"); if (country){ rule.setattributens("http://www.xulplanet.com/rdf/", "country", country); } else { rule.removeattributens("http://www.xulplanet.com/rdf/", "country"); } document.getelementbyid("photoslist").builder.rebuild(); } this version of the applyfilter function only needs to set or remove the attribute on the rule as necessary.

Sorting Results - Archive of obsolete content
changing the sort to change the sorting for a template's generated contents, you can either change the sort related attributes and rebuild the template, or you can call the sort method of the sort service: var listbox = document.getelementbyid("alistbox"); var sortservice = components.classes["@mozilla.org/xul/xul-sort-service;1"].

Template Logging - Archive of obsolete content
however, calling getelementbyid using this id will retrieve the generated content for that result if you want to further study the content that was generated.

Things I've tried to do with XUL - Archive of obsolete content
var available_width = document.getelementbyid("invisible_element").clientwidth; ...

Code Samples - Archive of obsolete content
change the first line to specify the page that you want to open: const url = "http://www.mozilla.org/" document .getelementbyid("content") .webnavigation .loaduri(url, 0, null, null, null) if your button is in thunderbird or sunbird, use code like this to open a web page.

Adding Event Handlers - Archive of obsolete content
the syntax is as follows: example 3 : source view <button id="okbutton" label="ok"/> <script> function buttonpressed(event){ alert('button was pressed!'); } var button = document.getelementbyid("okbutton"); button.addeventlistener('command', buttonpressed, true); </script> the getelementbyid() function returns the element with a given id, in this case the button.

Adding Labels and Images - Archive of obsolete content
</description> you can set the text via script using the textcontent property, as in the following example: <description id="text" width="200"/> document.getelementbyid('text').textcontent = "some lengthy word wrapped text goes here."; internally, both the label element and the description elements are the same.

Adding Methods to XBL-defined Elements - Archive of obsolete content
xul: <box id="num" class="labeledbutton" title="number of things:" value="52"/> <button label="show" oncommand="document.getelementbyid('num').showtitle(true)"/> <button label="hide" oncommand="document.getelementbyid('num').showtitle(false)"/> xbl: <binding id="labeledbutton"> <content> <xul:label xbl:inherits="value=title"/> <xul:label xbl:inherits="value"/> </content> <implementation> <method name="showtitle"> <parameter name="state"/> <body> if (state) { document.getanonymousn...

Broadcasters and Observers - Archive of obsolete content
example 3 : source view <broadcasterset> <broadcaster id="colorchanger" style="color: black"/> </broadcasterset> <button label="test"> <observes element="colorchanger" attribute="style" onbroadcast="alert('color changed');"/> </button> <button label="observer" oncommand="document.getelementbyid('colorchanger').setattribute('style','color: red');" /> two buttons have been created, one labeled test and the other labeled observer.

More Wizards - Archive of obsolete content
wizard example source <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <wizard id="thewizard" title="secret code wizard" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> function checkcode(){ document.getelementbyid('thewizard').canadvance = (document.getelementbyid('secretcode').value == "cabbage"); } </script> <wizardpage onpageshow="checkcode(); return true;"> <label value="enter the secret code:"/> <textbox id="secretcode" onkeyup="checkcode();"/> </wizardpage> <wizardpage> <label value="that is the correct secret code."/> </wizardpage> </wizard> there is also a correspon...

XPCOM Examples - Archive of obsolete content
<script> function getcookies() { var menu = document.getelementbyid("cookiemenu"); menu.removeallitems(); var cookiemanager = components.classes["@mozilla.org/cookiemanager;1"] .getservice(components.interfaces.nsicookiemanager); var iter = cookiemanager.enumerator; while (iter.hasmoreelements()){ var cookie = iter.getnext(); if (cookie instanceof components.interfaces.nsicookie){ if (cookie.host == "www.mozillazine...

Using Remote XUL - Archive of obsolete content
<?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script type="application/javascript"> function loadurl(event) { var contentframe = document.getelementbyid("contentframe"); var url = event.target.getattribute("value"); if (url) contentframe.setattribute("src", url); } </script> ...

XUL element attributes - Archive of obsolete content
you can use this as a parameter to getelementbyid() and other dom functions and to reference the element in style sheets.

description - Archive of obsolete content
</description> this is a long section of text that will not word wrap <description value="this is a long section of text that will not word wrap"> </description> this is a long section of dynamically controlled text that will word wrap <description id="desc" style="width: 300px"></description> document.getelementbyid('desc').textcontent = "this is a long section of dynamic message text that will word wrap"; attributes crop type: one of the values below if the label of the element is too big to fit in its given space, the text will be cropped on the side specified by the crop attribute.

editor - Archive of obsolete content
ocument, contentwindow, docshell, editingsession, editortype, webbrowserfind, webnavigation methods geteditor, gethtmleditor, makeeditable examples this example shows how to made the editor editable by setting the designmode property of the loaded html document: <script language="javascript"> function initeditor(){ // this function is called to set up the editor var editor = document.getelementbyid("myeditor"); editor.contentdocument.designmode = 'on'; } </script> <editor id="myeditor" editortype="html" src="about:blank" flex="1" type="content-primary"/> once editable, the document can have special formatting and other html pieces added to it using the document.execcommand method: var editor = document.getelementbyid("myeditor"); // toggle bold for the current selection editor.c...

iframe - Archive of obsolete content
ue="http://mozilla.org" /> <menuitem label="slashdot" value="http://slashdot.org"/> <menuitem label="sourceforge" value="http://sf.net" /> <menuitem label="freshmeat" value="http://freshmeat.net"/> </menupopup> </menulist> <iframe id="myframe" flex="1"/> <script> function donav(obj) { var url = obj.selecteditem.value; // note the firstchild is the menupopup element document.getelementbyid('myframe').setattribute('src', url); } </script> attributes showcaret type: boolean whether or not to cause a typing caret to be visible in the content area.

key - Archive of obsolete content
for example: // modify some attributes let key = document.getelementbyid(key_id); key.setattribute("modifiers", "alt shift"); // apply the changes let keyset = document.getelementbyid(keyset_id); keyset.parentnode.appendchild(keyset); ...

listbox - Archive of obsolete content
abel="ruby"/> <listitem label="emerald"/> <listitem label="sapphire" selected="true"/> <listitem label="diamond"/> </listbox> <listbox id="thelist" rows="10" width="400"> <listhead> <listheader label="1ct gem" width="240"/> <listheader label="price" width="150"/> </listhead> <listcols> <listcol/> <listcol flex="1"/> </listcols> </listbox> var thelist = document.getelementbyid('thelist'); gems = [ {gem: "ruby", price: "$3,500 - $4,600"}, {gem: "emerald", price: "$700 - 4,250"}, {gem: "blue sapphire", price: "$3,400 - $4,500"}, {gem: "diamond", price: "$5,600 - $16,000"} ]; for (var i = 0; i < gems.length; i++) { var row = document.createelement('listitem'); var cell = document.createelement('listcell'); cell.setattrib...

progressmeter - Archive of obsolete content
erties accessibletype, max, mode, value examples <progressmeter mode="determined" value="82"/> <progressmeter mode="undetermined"/> <!-- switching modes while the mouse is over a button --> <progressmeter mode="determined" id="myprogress"/> <button label="example" onmouseover="setloading(true)" onmouseout="setloading(false)"/> function setloading(state){ document.getelementbyid('myprogress').mode = (state) ?

window - Archive of obsolete content
you can use this as a parameter to getelementbyid() and other dom functions and to reference the element in style sheets.

wizard - Archive of obsolete content
ount, pageindex, pagestep, title, wizardpages methods advance, cancel, extra1, extra2, getbutton, getpagebyid, goto, rewind examples <?xml version="1.0"?> <?xml-stylesheet href="chrome://global/skin/" type="text/css"?> <wizard id="thewizard" title="secret code wizard" xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"> <script> function checkcode(){ document.getelementbyid('thewizard').canadvance = (document.getelementbyid('secretcode').value == "cabbage"); } </script> <wizardpage onpageshow="checkcode();"> <label value="enter the secret code:"/> <textbox id="secretcode" onkeyup="checkcode();"/> </wizardpage> <wizardpage> <label value="that is the correct secret code."/> </wizardpage> </wizard> attributes activetitlebarcolor type...

Building XULRunner with Python - Archive of obsolete content
for example def onload(): btntest = document.getelementbyid("btntest") btntest.addeventlistener('command', ontest, false) def ontest(): window.alert('button activated') window.addeventlistener('load', onload, false) one possible gotcha is that the default python path used to find modules that areimported explicitly includes the xulrunner executable directory and the directory that is current when xulrunner launches.

Getting started with XULRunner - Archive of obsolete content
main.js: function showmore() { document.getelementbyid("more-text").hidden = false; } for more information about xul see: xul.

xbDesignMode.js - Archive of obsolete content
* * contributor(s): doron rosenberg <doron@netscape.com> (original author) * * * * ***** end license block ***** */ /* xbdesignmode a javascript wrapper for browsers that support designmode */ function xbdesignmode(aiframe){ this.meditordocument = null; this.miframeelement = null; // argument is a string, therefore an id if ( (typeof(aiframe) == "string") && (document.getelementbyid(aiframe).tagname.tolowercase()=="iframe") ){ this.miframeelement = document.getelementbyid(aiframe); } else if( (typeof(aiframe)=="object") && (aiframe.tagname.tolowercase() == "iframe") ){ this.miframeelement = aiframe; } else { throw "argument isn't an id of an iframe or an iframe reference"; } if (this.miframeelement.contentdocument){ // gecko this.meditordocument ...

Adobe Flash - Archive of obsolete content
var myflash = document.getelementbyid("myflash").setvariable("myvar", sendtext); a more expanded code example that shows how example 2 was created is shown in this source listing.

Summary of Changes - Archive of obsolete content
tml 4.01 object deprecated applet html 4.01 object non-standard marquee html 4.01 div plus scripting non-standard bgsound html 4.01 object proprietary or deprecated feature w3c feature or recommended replacement ie5+ id_attribute_value document.all.id_attribute_value document.all[id_attribute_value] dom level 2: document.getelementbyid(id_attribute_value) ie5+ formname.inputname.value dom level 1: document.forms["formname"].inputname.value ie5+ inputname.value dom level 1: document.forms["formname"].inputname.value ie5+ formctrlname dom level 1: document.forms["formname"].formctrlname ie5+ document.forms(0) dom level 1: document.forms[0] ie...

RDF in Mozilla FAQ - Archive of obsolete content
*/; // get the dom element for 'my-tree' var tree = document.getelementbyid('my-tree'); // add our datasource to it tree.database.adddatasource(ds); // force the tree to rebuild *now*.

Windows Media in Netscape - Archive of obsolete content
instead of doing that, this is the recommendation and workaround for netscape 7.1: <script for="player" event="scriptcommand(type, param)"> if (type == "text") { var cap = document.getelementbyid("captext"); cap.innerhtml = param; } </script> more detailed examples are available in the final section on examples and sample code.

Building up a basic demo with Babylon.js - Game development
html structure here's the html structure we will use: <!doctype html> <html> <head> <meta charset="utf-8"> <title>mdn games: babylon.js demo</title> <style> html,body,canvas { margin: 0; padding: 0; width: 100%; height: 100%; font-size: 0; } </style> </head> <body> <script src="babylon.js"></script> <canvas id="render-canvas"></canvas> <script> var canvas = document.getelementbyid("render-canvas"); /* all our javascript code goes here */ </script> </body> </html> it contains some basic information like the document <title>, and some css to set the width and height of the <canvas> element (which babylon.js will use to render the content on) to fill the entire available viewport space.

Building up a basic demo with the PlayCanvas engine - Game development
<!doctype html> <html> <head> <meta charset="utf-8"> <title>mdn games: playcanvas demo</title> <style> body { margin: 0; padding: 0; } canvas { width: 100%; height: 100%; } </style> </head> <body> <script src="playcanvas-latest.js"></script> <canvas id="application-canvas"></canvas> <script> var canvas = document.getelementbyid("application-canvas"); /* all our javascript code goes here */ </script> </body> </html> it contains some basic information like the document <title>, and some css to set the width and height of the <canvas> element that playcanvas will use to 100% so that it will fill the entire available viewport space.

Audio for Web games - Game development
let's add some javascript to make this work: var myaudio = document.getelementbyid('myaudio'); var buttons = document.getelementsbytagname('button'); var stoptime = 0; for (var i = 0; i < buttons.length; i++) { buttons[i].addeventlistener('click', function() { myaudio.currenttime = this.getattribute("data-start"); stoptime = this.getattribute("data-stop"); myaudio.play(); }, false); } myaudio.addeventlistener('timeupdate', function() { if (this.currenttime >...

Crisp pixel art look with image-rendering - Game development
anvas: <canvas id="game" width="128" height="128"></canvas> css to size the canvas and render a crisp image: canvas { width: 512px; height: 512px; image-rendering: -moz-crisp-edges; image-rendering: -webkit-crisp-edges; image-rendering: pixelated; image-rendering: crisp-edges; } and some javascript to set up the canvas and load the image: // get canvas context var ctx = document.getelementbyid('game').getcontext('2d'); // load image var image = new image(); image.onload = function () { // draw the image into the canvas ctx.drawimage(image, 0, 0); } image.src = 'https://udn.realityripple.com/samples/11/a2954fe197.png'; this code used together produces the following result: note: you can check out the original code on github (and a live example.) ...

Create the Canvas and draw on it - Game development
var canvas = document.getelementbyid("mycanvas"); var ctx = canvas.getcontext("2d"); here we're storing a reference to the <canvas> element to the canvas variable.

Plug-in Development Overview - Gecko Plugin API Reference
consider the following example, where a media player plug-in can be controlled with an advancetonextsong() method called inside the script element: <object id="myplugin" type="audio/wav" data="music.wav"> </object> <script type="application/javascript"> var theplugin = document.getelementbyid('myplugin'); if (theplugin && theplugin.advancetonextsong) theplugin.advancetonextsong(); else alert("plugin not installed correctly"); </script> in the past, liveconnect and later xpconnect were used to make plug-ins scriptable.

jQuery - MDN Web Docs Glossary: Definitions of Web-related terms
$(document).ready(function(){ alert("hello world!"); $("#blackbox").hide(); }); the above code carries out the same function as the following code: window.onload = function() { alert("hello world!"); document.getelementbyid("blackbox").style.display = "none"; }; or: window.addeventlistener("load", () => { alert("hello world!"); document.getelementbyid("blackbox").style.display = "none"; }); learn more general knowledge jquery on wikipedia jquery official website technical information offical api reference documentation ...

Fundamental text and font styling - Learn web development
p { } </textarea> <h2>output</h2> <div class="output" style="width: 90%;height: 10em;padding: 10px;border: 1px solid #0095dd;"></div> <div class="controls"> <input id="reset" type="button" value="reset" style="margin: 10px 10px 0 0;"> </div> </div> const htmlinput = document.queryselector(".html-input"); const cssinput = document.queryselector(".css-input"); const reset = document.getelementbyid("reset"); let htmlcode = htmlinput.value; let csscode = cssinput.value; const output = document.queryselector(".output"); const styleelem = document.createelement('style'); const headelem = document.queryselector('head'); headelem.appendchild(styleelem); function drawoutput() { output.innerhtml = htmlinput.value; styleelem.textcontent = cssinput.value; } reset.addeventlistener("click", fun...

Styling links - Learn web development
0em;padding: 10px;border: 1px solid #0095dd;"></div> <div class="controls"> <input id="reset" type="button" value="reset" style="margin: 10px 10px 0 0;"> <input id="solution" type="button" value="show solution" style="margin: 10px 0 0 10px;"> </div> </div> var htmlinput = document.queryselector(".html-input"); var cssinput = document.queryselector(".css-input"); var reset = document.getelementbyid("reset"); var htmlcode = htmlinput.value; var csscode = cssinput.value; var output = document.queryselector(".output"); var solution = document.getelementbyid("solution"); var styleelem = document.createelement('style'); var headelem = document.queryselector('head'); headelem.appendchild(styleelem); function drawoutput() { output.innerhtml = htmlinput.value; styleelem.textcontent = cssinput...

Styling lists - Learn web development
px;border: 1px solid #0095dd;overflow: auto;"></div> <div class="controls"> <input id="reset" type="button" value="reset" style="margin: 10px 10px 0 0;"> <input id="solution" type="button" value="show solution" style="margin: 10px 0 0 10px;"> </div> </div> var htmlinput = document.queryselector(".html-input"); var cssinput = document.queryselector(".css-input"); var reset = document.getelementbyid("reset"); var htmlcode = htmlinput.value; var csscode = cssinput.value; var output = document.queryselector(".output"); var solution = document.getelementbyid("solution"); var styleelem = document.createelement('style'); var headelem = document.queryselector('head'); headelem.appendchild(styleelem); function drawoutput() { output.innerhtml = htmlinput.value; styleelem.textcontent = cssinput...

UI pseudo-classes - Learn web development
now finally, we've used some javascript to toggle the disabling of the billing address fields: // wait for the page to finish loading document.addeventlistener('domcontentloaded', function () { // attach `change` event listener to checkbox document.getelementbyid('billing-checkbox').addeventlistener('change', togglebilling); }, false); function togglebilling() { // select the billing text fields let billingitems = document.queryselectorall('#billing input[type="text"]'); // select the billing text labels let billinglabels = document.queryselectorall('.billing-label'); // toggle the billing text fields and labels for (let i = 0; i < billingit...

Adding vector graphics to the Web - Learn web development
svg> </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution" disabled> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); const output = document.queryselector('.output'); let code = textarea.value; let userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentr...

From object to iframe — other embedding technologies - Learn web development
ght: 100px;"> </textarea> <div class="playable-buttons"> <input id="reset" type="button" value="reset"> <input id="solution" type="button" value="show solution"> </div> html { font-family: sans-serif; } h2 { font-size: 16px; } .a11y-label { margin: 0; text-align: right; font-size: 0.7rem; width: 98%; } body { margin: 10px; background: #f5f9fa; } const textarea = document.getelementbyid('code'); const reset = document.getelementbyid('reset'); const solution = document.getelementbyid('solution'); const output = document.queryselector('.output'); let code = textarea.value; let userentry = textarea.value; function updatecode() { output.innerhtml = textarea.value; } reset.addeventlistener('click', function() { textarea.value = code; userentry = textarea.value; solutionentr...

Video and audio content - Learn web development
restarting media playback at any time, you can reset the media to the beginning—including the process of selecting the best media source, if more than one is specified using <source> elements—by calling the element's load() method: const mediaelem = document.getelementbyid("my-media-element"); mediaelem.load(); detecting track addition and removal you can monitor the track lists within a media element to detect when tracks are added to or removed from the element's media.

Choosing the right approach - Learn web development
we then run it once per second using setinterval(), creating the effect of a digital clock that updates once per second (see this live, and also see the source): function displaytime() { let date = new date(); let time = date.tolocaletimestring(); document.getelementbyid('demo').textcontent = time; } const createclock = setinterval(displaytime, 1000); pitfalls the frame rate isn't optimized for the system the animation is running on, and can be somewhat inefficient.

Cooperative asynchronous JavaScript: Timeouts and intervals - Learn web development
it then runs the function once per second using setinterval(), creating the effect of a digital clock that updates once per second (see this live, and also see the source): function displaytime() { let date = new date(); let time = date.tolocaletimestring(); document.getelementbyid('demo').textcontent = time; } const createclock = setinterval(displaytime, 1000); just like settimeout(), setinterval() returns an identifying value you can use later when you need to clear the interval.

Introduction to events - Learn web development
if they are, we call the preventdefault() function on the event object — which stops the form submission — and then display an error message in the paragraph below our form to tell the user what's wrong: const form = document.queryselector('form'); const fname = document.getelementbyid('fname'); const lname = document.getelementbyid('lname'); const para = document.queryselector('p'); form.onsubmit = function(e) { if (fname.value === '' || lname.value === '') { e.preventdefault(); para.textcontent = 'you need to fill in both names!'; } } obviously, this is pretty weak form validation — it wouldn't stop the user validating the form with spaces or numbers entered i...

Solve common problems in your JavaScript code - Learn web development
some common built-in browser functions that cause problems are: correct wrong getelementsbytagname() getelementbytagname() getelementsbyname() getelementbyname() getelementsbyclassname() getelementbyclassname() getelementbyid() getelementsbyid() semi-colon position you need to make sure you don't place any semi-colons incorrectly.

Componentizing our React app - Learn web development
the final line of src/index.js should read like this: reactdom.render(<app tasks={data} />, document.getelementbyid("root")); this array is now available to the app component as props.tasks.

Focus management with Vue refs - Learn web development
however, it also means you often should not edit your html elements directly through native browser apis (like document.getelementbyid) when using frameworks, because it results in the vdom and real dom going out of sync.

Implementing feature detection - Learn web development
script inside the tags: if (modernizr.geolocation) { navigator.geolocation.getcurrentposition(function(position) { let latlng = new google.maps.latlng(position.coords.latitude,position.coords.longitude); let myoptions = { zoom: 8, center: latlng, maptypeid: google.maps.maptypeid.terrain, disabledefaultui: true } let map = new google.maps.map(document.getelementbyid("map_canvas"), myoptions); }); } else { const para = document.createelement('p'); para.textcontent = 'argh, no geolocation!'; document.body.appendchild(para); } try your example out!

Handling common HTML and CSS problems - Learn web development
store a reference to this element in a variable, for example: const test = document.getelementbyid('hplogo'); now try to set a new value for the css property you are interested in on that element; you can do this using the style property of the element, for example try typing these into the javascript console: test.style.transform = 'rotate(90deg)' test.style.webkittransform = 'rotate(90deg)' as you start to type the property name representation after the second dot (note that in java...

A bird's-eye view of the Mozilla framework
var toctree = document.getelementbyid("help-toc-panel"); the document object is a xuldocument, and toctree is thecontents panel xulelement.

Cross Process Object Wrappers
*/ var button = content.document.getelementbyid("click-me"); button.addeventlistener("mouseover", function (event) { sendasyncmessage("my-addon-message", {}, { element : event.target }); }, false); // chrome script /* load the frame script, then listen for the message.

MozBeforePaint
<!doctype html> <html> <body> <div id="d" style="width:100px; height:100px; background:lime; position:relative;"></div> <script> var d = document.getelementbyid("d"); var start = window.mozanimationstarttime; function step(event) { var progress = event.timestamp - start; d.style.left = math.min(progress/10, 200) + "px"; if (progress < 2000) { window.mozrequestanimationframe(); } else { window.removeeventlistener("mozbeforepaint", step, false); } } window.addeventlistener("mozbeforepaint", step, false); window.mozrequestanimationframe();...

Localization and Plurals
er of files # example: 111 files - downloads downloadstitlefiles=#1 file - downloads;#1 files - downloads # localization note (timepair): #1 time number; #2 time unit # example: 1 second; 11 seconds timepair=#1 #2 seconds=second;seconds minutes=minute;minutes hours=hour;hours downloads.js: components.utils.import("resource://gre/modules/pluralform.jsm"); let getstr = function(string) document.getelementbyid("strings").getstring(string); // get the correct plural form for the title let numdownloads = 3; let title = pluralform.get(numdownloads, getstr("downloadstitlefiles")); // put in the correct number of downloads print(title.replace("#1", numdownloads)); // get the correct plural form of seconds let timeleft = 55; let seconds = pluralform.get(timeleft, getstr("seconds")); // print the localized ...

Extras
mi>n</mi> <mo>!</mo> </mrow> </mfrac> </mrow> </math> </foreignobject> <text>exp(α)</text> </switch> </g> </g> </svg> </div> inline javascript html content <math display="block"> <mfrac> <mtext id="num">mouse</mtext> <mtext id="denum">over</mtext> </mfrac> </math> javascript content function whoistherealert(evt) { alert("who is there?"); } function attachlistener(id) { document.getelementbyid(id).addeventlistener("mouseover", whoistherealert); } function init() { attachlistener("num"); attachlistener("denum"); } window.addeventlistener("load", init); ...

MathML Torture Test
th { font-family: stix two math; } .texgyrebonum math { font-family: tex gyre bonum math; } .texgyrepagella math { font-family: tex gyre pagella math; } .texgyreschola math { font-family: tex gyre schola math; } .texgyretermes math { font-family: tex gyre termes math; } .xits math { font-family: xits math; } javascript content function updatemathfont() { var mathfont = document.getelementbyid("mathfont").value; if (mathfont == "default") { document.body.removeattribute("class"); } else { document.body.setattribute("class", mathfont); } } function load() { document.getelementbyid("mathfont").

MathML In Action
/mn> <mi>a</mi> </mrow> </mfrac> </mrow> </mstyle> </math> </p> javascript content function zoomtoggle() { if (this.hasattribute("mathsize")) { this.removeattribute("mathsize"); } else { this.setattribute("mathsize", "200%"); } } function load() { document.getelementbyid("zoomablemath").

javascript.options.strict
var name2= "peter"; document.getelementbyid("sample").innerhtml = name1; </script> </body> </html> possible values and their effects: true: show javascript errors and warnings.

Building the WebLock UI
in this tutorial, focusing as it is on the weblock functionality (rather than the ui), we'll assume the strings we get from the ui itself are urls we actually want to write to the white list: function addthissite() { var tf = document.getelementbyid("dialog.input"); // weblock is global and declared above weblock.addsite(tf.value); } this javascript function can be called directly from the xul widget, where the input string is retrieved as the value property of the textbox element.

Introduction to XPCOM for the DOM
for example, in idl we'd write getelementbyid, which in c++ would be translated to getelementbyid.

nsIFileView
opriate id is passed, nsifileview relies on the treecols section --> <treecol id="filenamecolumn" label="name" flex="1" primary="true"/> <treecol id="lastmodifiedcolumn" label="date" flex="1"/> <treecol id="size" label="size" flex="1"/> </treecols> <treechildren/> </tree> <script> var dir="/home/"; //the directory to be opened var ftree = document.getelementbyid("ftree"); //the xul tree element var lfile = components.classes["@mozilla.org/file/local;1"] .createinstance(components.interfaces.nsilocalfile); lfile.initwithpath(dir); // open the directory var fview = components.classes["@mozilla.org/filepicker/fileview;1"] .createinstance(components.interfaces.nsifileview); //create an instance of the component tview = fview.query...

Using nsISimpleEnumerator
using nsisimpleenumerator <stringbundle>.strings var enumerator = document.getelementbyid('astringbundleid').strings; var s = ""; while (enumerator.hasmoreelements()) { var property = enumerator.getnext().queryinterface(components.interfaces.nsipropertyelement); s += property.key + ' = ' + property.value + ';\n'; } alert(s); example using javascript 1.7 features // creates a generator iterating over enum's values function generatorfromsimpleenumerator(enum, interface) { while (enum.hasmoreelements()) { yield enum.getnext().queryinterface(interface); } } var b = document.getelementbyid("stringbundleset").firstchild var props = generatorfromenumerator(b.strings, components.interfaces.nsipropertyelement); var s = ""; for (let property in props) { s += property.key + ' = ' + pr...

Filelink Providers
for example, the hightail implementation provides the following function: function extraargs() { var usernamevalue = document.getelementbyid("username").value; return { "username": {type: "char", value: usernamevalue}, }; } in this example, the username value is read from the input, and then the specially-crafted object is returned.

Adding items to the Folder Pane
the following code snippet listens for that event: let gnumbersext = { load: function gne_load() { window.removeeventlistener("load", gnumbersext.load, false); let tree = document.getelementbyid("foldertree"); tree.addeventlistener("maprebuild", gnumbersext._insert, false); }, _insert: function gne__insert() { // this function is called when a rebuild occurs } }; window.addeventlistener("load", gnumbersext.load, true); the structure of folder-tree-items the folder pane stores its current display data in a property called _rowmap.

Building a Thunderbird extension 6: Adding JavaScript
window.addeventlistener("load", function(e) { startup(); }, false); window.setinterval( function() { startup(); }, 60000); //update date every minute function startup() { var mypanel = document.getelementbyid("my-panel"); var date = new date(); var day = date.getday(); var datestring = date.getfullyear() + "." + (date.getmonth()+1) + "." + date.getdate(); mypanel.label = "date: " + datestring; } the first part registers a new event listener that will be executed automatically when thunderbird loads.

Access StringBundle from Overlay
the most efficient way to append these strings is by attaching them to an existing stringbundleset as such: <stringbundleset id="stringbundleset"> <stringbundle src="chrome://your_extension/locale/overlay.properties" id="your-extension-strings" /> </stringbundleset> now that your stringbundle is attached you can access it from javascript as follows: var str = document.getelementbyid("your-extension-strings"); //get the stringbundle object itself str.getstring("propertyname"); //get a string (and do something with it) alternative way let stringbundleservice = cc["@mozilla.org/intl/stringbundle;1"].getservice(ci.nsistringbundleservice); let bundle = stringbundleservice.createbundle("chrome://your_extension/locale/overlay.properties"); let s...

Add New Tab
var aurl = "chrome://myext/mytab.xul"; let tabmail = getmail3pane().document.getelementbyid("tabmail"); tabmail.opentab("chrometab", { chromepage: aurl }); ...

Detect Opening Folder
to do this you need to capture the select event of the folder [[xul:tree|tree]] whose id is (conveniently) foldertree like so: window.document.getelementbyid('foldertree').addeventlistener("select", testcolumns, false); ...

customDBHeaders Preference
onents.interfaces.nsiobserver observe: function(amsgfolder, atopic, adata) { dump("here here!"); addcustomcolumnhandler(); } } function doonceloaded(){ var observerservice = components.classes["@mozilla.org/observer-service;1"].getservice(components.interfaces.nsiobserverservice); observerservice.addobserver(createdbobserver, "msgcreatedbview", false); window.document.getelementbyid('foldertree').addeventlistener("select",addcustomcolumnhandler,false); } window.addeventlistener("load",doonceloaded,false); dump(" ~ ~ ~ ~ end superfluous ~ ~ ~ ~ \n"); important be aware that only messages that are added to the .msf database after the customdbheaders pref is set will have the corresponding string property set on the msghdr.

Using popup notifications
components.utils.import('resource://gre/modules/popupnotifications.jsm'); var notify = new popupnotifications(gbrowser, document.getelementbyid("notification-popup"), document.getelementbyid("notification-popup-box")); var notification = notify.show( // browser gbrowser.selectedbrowser, // popup id "pdes-popup", // message "hi, there!, i'm gonna show you something today!!", // anchor id null, // main action { label: "click here", accesskey: "d", callback: function() { // you can call your functio...

Plug-in Development Overview - Plugins
consider the following example, where a media player plug-in can be controlled with an advancetonextsong() method called inside the script element: <object id="myplugin" type="audio/wav" data="music.wav"> </object> <script type="application/javascript"> var theplugin = document.getelementbyid('myplugin'); if (theplugin && theplugin.advancetonextsong) theplugin.advancetonextsong(); else alert("plugin not installed correctly"); </script> in the past, liveconnect and later xpconnect were used to make plug-ins scriptable.

Browser Console - Firefox Developer Tools
on windows, the following code will add a new item to the browser's main menu: var parent = window.document.getelementbyid("appmenuprimarypane"); var makethetea = gbrowser.ownerdocument.defaultview.document.createelementns("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul", "menuitem"); makethetea.setattribute("label", "a nice cup of tea?"); parent.appendchild(makethetea); on macos, this similar code will add a new item to the "tools" menu: var parent = window.document.getelementbyid("menu_toolspopup")...

Debug eval sources - Firefox Developer Tools
in the video below, we load a page containing a source like this: var script = `function foo() { console.log('called foo'); } //# sourceurl=my-foo.js`; eval(script); var button = document.getelementbyid("foo"); button.addeventlistener("click", foo, false); the evaluated string is given the name "my-foo.js" using the //# sourceurl directive.

DOM allocation example - Firefox Developer Tools
turn toolbarbutton; } function createtoolbar() { var toolbar = document.createelement("div"); // stop spidermonkey from sharing instances toolbar[getrandomint(0,5000)] = "foo"; for (var i = 0; i < toolbarbuttoncount; i++) { var toolbarbutton = createtoolbarbutton(); toolbar.appendchild(toolbarbutton); } return toolbar; } function createtoolbars() { var container = document.getelementbyid("container"); for (var i = 0; i < toolbarcount; i++) { var toolbar = createtoolbar(); container.appendchild(toolbar); } } createtoolbars(); a simple pseudocode representation of how this code operates looks like this: createtoolbars() -> createtoolbar() // called 200 times, creates 1 div element each time -> createtoolbarbutton() // called 20 times per toolbar, creates 1...

Monster example - Firefox Developer Tools
dly": [], "fierce": [], "undecided": [] }; for (var i = 0; i &lt; monster_count; i++) { monsters.friendly.push(new monster()); } for (var i = 0; i &lt; monster_count; i++) { monsters.fierce.push(new monster()); } for (var i = 0; i &lt; monster_count; i++) { monsters.undecided.push(new monster()); } console.log(monsters); } var makemonstersbutton = document.getelementbyid("make-monsters"); makemonstersbutton.addeventlistener("click", makemonsters); the page contains a button: when you push the button, the code creates some monsters.

Animation inspector example: CSS transitions - Firefox Developer Tools
an { opacity: 1; width: 300px; } javascript content function toggleselection(e) { if (e.button != 0) { return; } if (e.target.classlist.contains("icon")) { var wasselected = (e.target.getattribute("id") == "selected"); clearselection(); if (!wasselected) { e.target.setattribute("id", "selected"); } } } function clearselection() { var selected = document.getelementbyid("selected"); if (selected) { selected.removeattribute("id"); } } document.addeventlistener("click", toggleselection); ...

Animation inspector example: Web Animations API - Firefox Developer Tools
)', offset: 0.666 }, { transform: 'scale(1.5)', filter: 'grayscale(0%)'} ]; var notekeyframeset = [ { opacity: '0', width: '0'}, { opacity: '1', width: '300px'} ]; var iconkeyframeoptions = { duration: 750, fill: 'forwards', easing: 'ease-in', enddelay: 100 } var notekeyframeoptions = { duration: 500, fill: 'forwards', easing: 'ease-out', delay: 150 } var icon = document.getelementbyid("icon"); var note = document.getelementbyid("note"); var iconanimation = icon.animate(iconkeyframeset, iconkeyframeoptions); var noteanimation = note.animate(notekeyframeset, notekeyframeoptions); iconanimation.pause(); noteanimation.pause(); var firsttime = true; function animatechannel(e) { if (e.button != 0) { return; } if (e.target.id != "icon") { return; } if (firsttime...

Waterfall - Firefox Developer Tools
for example, consider code like this: var timerbutton = document.getelementbyid("timer"); timerbutton.addeventlistener("click", handleclick, false); function handleclick() { console.time("timer"); runtimer(1000).then(timerfinished); } function timerfinished() { console.timeend("timer"); console.log("ready!"); } function runtimer(t) { return new promise(function(resolve) { settimeout(resolve, t); }); } the waterfall will display a marker for the period bet...

Console messages - Firefox Developer Tools
for example, code like this will cause an immediate, synchronous, reflow, when it calls window.getcomputedstyle(thing).height: var thing = document.getelementbyid("the-thing"); thing.style.display = "inline-block"; var thingheight = window.getcomputedstyle(thing).height; because of this, it's a good idea to avoid interleaving write and read calls to an element's styles when manipulating the dom, because every time you read back a style that has been invalidated by a previous write call, you force a synchronous reflow.

The JavaScript input interpreter - Firefox Developer Tools
there are three ways to select an iframe using cd(): you can pass the iframe dom element: var frame = document.getelementbyid("frame1"); cd(frame); you can pass a css selector that matches the iframe: cd("#frame1"); you can pass the iframe's global window object: var frame = document.getelementbyid("frame1"); cd(frame.contentwindow); to switch the context back to the top-level window, call cd() with no arguments: cd(); for example, suppose we have a document that embeds an iframe: <!doctype html> <html> <head...

AddressErrors - Web APIs
window.addeventlistener("load", function(ev) { document.getelementbyid("pay").addeventlistener("click", process, false); }, false); see addeventlistener() for information about event handlers and how they work.

AnalyserNode - Web APIs
analyser.fftsize = 2048; var bufferlength = analyser.frequencybincount; var dataarray = new uint8array(bufferlength); analyser.getbytetimedomaindata(dataarray); // get a canvas defined with id "oscilloscope" var canvas = document.getelementbyid("oscilloscope"); var canvasctx = canvas.getcontext("2d"); // draw an oscilloscope of the current audio source function draw() { requestanimationframe(draw); analyser.getbytetimedomaindata(dataarray); canvasctx.fillstyle = "rgb(200, 200, 200)"; canvasctx.fillrect(0, 0, canvas.width, canvas.height); canvasctx.linewidth = 2; canvasctx.strokestyle = "rgb(0, 0, 0)"; canvasctx.begi...

Animation.onfinish - Web APIs
here is one instance where we add pointer events back to an element after its opacity animation has faded it in: // add an animation to the game's ending credits var endingui = document.getelementbyid("ending-ui"); var bringui = endingui.animate(keysfade, timingfade); // pause said animation's credits bringui.pause(); // this function removes pointer events on the credits.

Animation.pause() - Web APIs
example animation.pause() is used many times in the alice in web animations api land growing/shrinking alice game, largely because animations created with the element.animate() method immediately start playing and must be paused manually if you want to avoid that: // animation of the cupcake slowly getting eaten up var nommingcake = document.getelementbyid('eat-me_sprite').animate( [ { transform: 'translatey(0)' }, { transform: 'translatey(-80%)' } ], { fill: 'forwards', easing: 'steps(4, end)', duration: alicechange.effect.timing.duration / 2 }); // doesn't actually need to be eaten until a click event, so pause it initially: nommingcake.pause(); additionally, when resetting : // an all-purpose function to pause the animations on ...

Animation.play() - Web APIs
two animation.play()s, one eventlistener: // the cake has its own animation: var nommingcake = document.getelementbyid('eat-me_sprite').animate( [ { transform: 'translatey(0)' }, { transform: 'translatey(-80%)' } ], { fill: 'forwards', easing: 'steps(4, end)', duration: alicechange.effect.timing.duration / 2 }); // pause the cake's animation so it doesn't play immediately.

Animation.startTime - Web APIs
examples in the running on web animations api example, the we can sync all new animated cats by giving them all the same starttime as the original running cat: var catrunning = document.getelementbyid ("withwaapi").animate(keyframes, timing); /* a function that makes new cats.

AudioScheduledSourceNode: ended event - Web APIs
examples in this simple example, an event listener for the ended event is set up to enable a "start" button in the user interface when the node stops playing: node.addeventlistener('ended', () => { document.getelementbyid("startbutton").disabled = false; }) you can also set up the event handler using the audioscheduledsourcenode.onended property: node.onended = function() { document.getelementbyid("startbutton").disabled = false; } for an example of the ended event in use, see our audio-buffer example on github.

AudioScheduledSourceNode.onended - Web APIs
node.onended = function(event) { document.getelementbyid("startbutton").disabled = false; } specifications specification status comment web audio apithe definition of 'onended' in that specification.

AudioTrack.enabled - Web APIs
function swapcommentarymain() { var videoelem = document.getelementbyid("main-video"); var audiotrackmain; var audiotrackcommentary; videoelem.audiotracks.foreach(track) { if (track.kind === "main") { audiotrackmain = track; } else if (track.kind === "commentary") { audiotrackcommentary = track; } } if (audiotrackmain && audiotrackcommentary) { var commentaryenabled = audiotrackcommentary.enabled; audiotrackcommentary.enabl...

Blob.size - Web APIs
// fileinput is a htmlinputelement: <input type="file" multiple id="myfileinput"> var fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (simliar to nodelist) var files = fileinput.files; for (var i = 0; i < files.length; i++) { console.log(files[i].name + " has a size of " + files[i].size + " bytes"); } specifications specification status comment file apithe definition of 'blob.size' in that specification.

Blob.type - Web APIs
var i, fileinput, files, allowedfiletypes; // fileinput is a htmlinputelement: <input type="file" multiple id="myfileinput"> fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (simliar to nodelist) files = fileinput.files; // our application only allows gif, png, and jpeg images allowedfiletypes = ["image/png", "image/jpeg", "image/gif"]; for (i = 0; i < files.length; i++) { // test if file.type is an allowed file type.

Body.body - Web APIs
const image = document.getelementbyid('target'); // fetch the original image fetch('./tortoise.png') // retrieve its body as readablestream .then(response => response.body) .then(body => { const reader = body.getreader(); return new readablestream({ start(controller) { return pump(); function pump() { return reader.read().then(({ done, value }) => { // when no more data needs to be consumed, c...

CSSKeywordValue.CSSKeywordValue() - Web APIs
#myelement { display: flex; } <div id="myelement">check the developer tools to see the log in the console and to inspect the style attribute on this div.</div> let keyword = new csskeywordvalue('initial'); let myelement = document.getelementbyid('myelement').attributestylemap; myelement.set('display', keyword); console.log( myelement.get('display').value); // 'initial' console.dir( keyword ); specifications specification status comment css typed om level 1the definition of 'csskeywordvalue' in that specification.

CSSKeywordValue.value - Web APIs
let indicator = document.getelementbyid('indicator'); indicator.attributestylemap.set('display', new csskeywordvalue('initial')); indicator.attributestylemap.get('display').value // 'initial' specifications specification status comment css typed om level 1the definition of 'undefined' in that specification.

CSSKeywordValue - Web APIs
#myelement { display: flex; } <div id="myelement">check the developer tools to see the log in the console and to inspect the style attribute on this div.</div> let myelement = document.getelementbyid('myelement').attributestylemap; myelement.set('display', new csskeywordvalue('initial')); console.log( myelement.get('display').value); // 'initial' specifications specification status comment css typed om level 1the definition of 'csskeywordvalue' in that specification.

CSSPositionValue.CSSPositionValue() - Web APIs
let somediv = document.getelementbyid('container'); let position = new csspositionvalue(css.px(5), css.px(10)); somediv.attributestylemap.set('object-position', position); console.log(position.x.value, position.y.value); // 5 10 ...

CSSPositionValue.x - Web APIs
let somediv = document.getelementbyid('container'); let position = new csspositionvalue(css.px(5), css.px(10)); somediv.attributestylemap.set('object-position', position); console.log(position.x.value, position.y.value); ...

CSSPositionValue.y - Web APIs
let replaceel = document.getelementbyid('container'); let position = new csspositionvalue(css.px(5), css.px(10)); somediv.attributestylemap.set('object-position', position); console.log(position.x.value, position.y.value); ...

CSSPositionValue - Web APIs
let replacedel = document.getelementbyid( 'image' ); let position = new csspositionvalue( css.px(35), css.px(40) ); replacedel.attributestylemap.set( 'object-position', position ); console.log( position.x.value, position.y.value ); console.log( replacedel.computedstylemap().get('object-position') ); we set the object-position property, then check the values returned.

CSSPrimitiveValue.getRectValue() - Web APIs
example var cs = window.getcomputedstyle(document.getelementbyid("clippeddiv")); var cssvalue = cs.getpropertycssvalue("clip"); console.log(cssvalue.getrectvalue()); specifications specification status comment document object model (dom) level 2 style specificationthe definition of 'cssprimitivevalue.getrectvalue' in that specification.

CSSStyleDeclaration.cssText - Web APIs
example <span id="s1" style="color: red;"> some text </span> <script> var elem = document.getelementbyid("s1"); alert(elem.style.csstext); // "color: red;" </script> specifications specification status comment css object model (cssom)the definition of 'cssstyledeclaration: csstext' in that specification.

CSSStyleDeclaration.item() - Web APIs
javascript has a special simpler syntax for obtaining an item from a nodelist by index: var propertyname = style[index]; example var style = document.getelementbyid('div1').style; var propertyname = style.item(1); // or simply style[1] - returns the second style listed specifications specification status comment css object model (cssom)the definition of 'cssstyledeclaration.item()' in that specification.

CSSStyleDeclaration.length - Web APIs
example the following gets the number of explicitly set styles on the following html element: <div id="div1" style="margin: 0 10px; background-color: #ca1; font-family: monospace"></div> javascript code: var mydiv = document.getelementbyid('div1'); var divstyle = mydiv.style; var len = divstyle.length; // 6 specifications specification status comment css object model (cssom)the definition of 'cssstyledeclaration.length' in that specification.

CanvasGradient.addColorStop() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let gradient = ctx.createlineargradient(0, 0, 200, 0); gradient.addcolorstop(0, 'green'); gradient.addcolorstop(.7, 'white'); gradient.addcolorstop(1, 'pink'); ctx.fillstyle = gradient; ctx.fillrect(10, 10, 200, 100); result specifications specification status comment html living standardthe definition of 'canvasgradie...

CanvasRenderingContext2D.beginPath() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // first path ctx.beginpath(); ctx.strokestyle = 'blue'; ctx.moveto(20, 20); ctx.lineto(200, 20); ctx.stroke(); // second path ctx.beginpath(); ctx.strokestyle = 'green'; ctx.moveto(20, 20); ctx.lineto(120, 120); ctx.stroke(); result specifications specification status comment html living standardthe definition of 'ca...

CanvasRenderingContext2D.canvas - Web APIs
you can get a reference to the canvas element within the canvasrenderingcontext2d by using the canvas property: var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.canvas // htmlcanvaselement specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.canvas' in that specification.

CanvasRenderingContext2D.clearHitRegions() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // set some hit regions ctx.addhitregion({id: 'eyes'}); ctx.addhitregion({id: 'nose'}); ctx.addhitregion({id: 'mouth'}); // remove them altogether from the canvas ctx.clearhitregions(); specifications canvas hit regions have been removed from the whatwg living standard, although discussions about future standardization are ongoing.

CanvasRenderingContext2D.createLinearGradient() - Web APIs
html <canvas id="canvas"></canvas> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); // create a linear gradient // the start gradient point is at x=20, y=0 // the end gradient point is at x=220, y=0 var gradient = ctx.createlineargradient(20,0, 220,0); // add three color stops gradient.addcolorstop(0, 'green'); gradient.addcolorstop(.5, 'cyan'); gradient.addcolorstop(1, 'green'); // set the fill style and draw a rectangle ctx.fill...

CanvasRenderingContext2D.createPattern() - Web APIs
the original image looks like this: html <canvas id="canvas" width="300" height="300"></canvas> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); var img = new image(); img.src = 'https://udn.realityripple.com/samples/04/aaeaf9aac4.png'; img.onload = function() { var pattern = ctx.createpattern(img, 'repeat'); ctx.fillstyle = pattern; ctx.fillrect(0, 0, 300, 300); }; creating a pattern from a canvas in this example we create a pattern from the contents of an offscreen canvas.

CanvasRenderingContext2D.createRadialGradient() - Web APIs
html <canvas id="canvas" width="200" height="200"></canvas> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); // create a radial gradient // the inner circle is at x=110, y=90, with radius=30 // the outer circle is at x=100, y=100, with radius=70 var gradient = ctx.createradialgradient(110,90,30, 100,100,70); // add three color stops gradient.addcolorstop(0, 'pink'); gradient.addcolorstop(.9, 'white'); gradient.addcolorstop(1, 'green'); // set the fill sty...

CanvasRenderingContext2D.currentTransform - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let matrix = ctx.currenttransform; matrix.a = 1; matrix.b = 1; matrix.c = 0; matrix.d = 1; matrix.e = 0; matrix.f = 0; ctx.currenttransform = matrix; ctx.fillrect(0, 0, 100, 100); result ...

CanvasRenderingContext2D.direction - Web APIs
html <canvas id="canvas"></canvas> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.font = '48px serif'; ctx.filltext('hi!', 150, 50); ctx.direction = 'rtl'; ctx.filltext('hi!', 150, 130); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.direction' in that specification.

CanvasRenderingContext2D.drawFocusIfNeeded() - Web APIs
html <canvas id="canvas"> <button id="button1">continue</button> <button id="button2">quit</button> </canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const button1 = document.getelementbyid('button1'); const button2 = document.getelementbyid('button2'); document.addeventlistener('focus', redraw, true); document.addeventlistener('blur', redraw, true); canvas.addeventlistener('click', handleclick, false); redraw(); function redraw() { ctx.clearrect(0, 0, canvas.width, canvas.height); drawbutt...

CanvasRenderingContext2D.font - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = 'bold 48px serif'; ctx.stroketext('hello world', 50, 100); result loading fonts with the css font loading api with the help of the fontface api, you can explicitly load fonts before using them in a canvas.

CanvasRenderingContext2D.getImageData() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.rect(10, 10, 100, 100); ctx.fill(); let imagedata = ctx.getimagedata(60, 60, 200, 100); ctx.putimagedata(imagedata, 150, 10); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.getimagedata' in that specification.

CanvasRenderingContext2D.getLineDash() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.setlinedash([10, 20]); console.log(ctx.getlinedash()); // [10, 20] // draw a dashed line ctx.beginpath(); ctx.moveto(0, 50); ctx.lineto(300, 50); ctx.stroke(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.getlinedash' in that specification.

CanvasRenderingContext2D.globalCompositeOperation - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.globalcompositeoperation = 'xor'; ctx.fillstyle = 'blue'; ctx.fillrect(10, 10, 100, 100); ctx.fillstyle = 'red'; ctx.fillrect(50, 50, 100, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.globalcompositeoperation' in that specification.

CanvasRenderingContext2D.imageSmoothingEnabled - Web APIs
html <canvas id="canvas" width="460" height="210"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.font = '16px sans-serif'; ctx.textalign = 'center'; const img = new image(); img.src = 'https://interactive-examples.mdn.mozilla.net/media/examples/star.png'; img.onload = function() { const w = img.width, h = img.height; ctx.filltext('source', w * .5, 20); ctx.drawimage(img, 0, 24, w, h); ctx.filltext('smoothing = true', w *...

CanvasRenderingContext2D.imageSmoothingQuality - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let img = new image(); img.src = 'https://mdn.mozillademos.org/files/222/canvas_createpattern.png'; img.onload = function() { ctx.imagesmoothingquality = 'low'; ctx.drawimage(img, 0, 0, 300, 150); }; result specifications specification status comment html living standardthe definition of 'imagesmoothingquality' in ...

CanvasRenderingContext2D.lineWidth - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.linewidth = 15; ctx.beginpath(); ctx.moveto(20, 20); ctx.lineto(130, 130); ctx.rect(40, 40, 70, 70); ctx.stroke(); result more examples for more examples and explanation about this property, see applying styles and color in the canvas tutorial.

CanvasRenderingContext2D.measureText() - Web APIs
you can get a textmetrics object using the following code: const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); let text = ctx.measuretext('hello world'); console.log(text.width); // 56; specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.measuretext' in that specification.

CanvasRenderingContext2D.miterLimit - Web APIs
playable code <canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas> <div class="playable-buttons"> <input id="edit" type="button" value="edit" /> <input id="reset" type="button" value="reset" /> </div> <textarea id="code" class="playable-code"> ctx.beginpath(); ctx.moveto(0,0); ctx.linewidth = 15; ctx.lineto(100, 100); ctx.stroke();</textarea> var canvas = document.getelementbyid("canvas"); var ctx = canvas.getcontext("2d"); var textarea = document.getelementbyid("code"); var reset = document.getelementbyid("reset"); var edit = document.getelementbyid("edit"); var code = textarea.value; function drawcanvas() { ctx.clearrect(0, 0, canvas.width, canvas.height); eval(textarea.value); } reset.addeventlistener("click", function() { textarea.value = code; drawcanvas()...

CanvasRenderingContext2D.moveTo() - Web APIs
var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(50, 50); // begin first sub-path ctx.lineto(200, 50); ctx.moveto(50, 90); // begin second sub-path ctx.lineto(280, 120); ctx.stroke(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.moveto' in that specification.

CanvasRenderingContext2D.putImageData() - Web APIs
html <canvas id="canvas"></canvas> javascript var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); function putimagedata(ctx, imagedata, dx, dy, dirtyx, dirtyy, dirtywidth, dirtyheight) { var data = imagedata.data; var height = imagedata.height; var width = imagedata.width; dirtyx = dirtyx || 0; dirtyy = dirtyy || 0; dirtywidth = dirtywidth !== undefined?

CanvasRenderingContext2D.rect() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.rect(10, 20, 150, 100); ctx.fill(); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.rect' in that specification.

CanvasRenderingContext2D.removeHitRegion() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // set a hit region ctx.addhitregion({id: 'eyes'}); // remove it from the canvas ctx.removehitregion('eyes'); specifications canvas hit regions have been removed from the whatwg living standard, although discussions about future standardization are ongoing.

CanvasRenderingContext2D.restore() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // save the default state ctx.save(); ctx.fillstyle = 'green'; ctx.fillrect(10, 10, 100, 100); // restore the default state ctx.restore(); ctx.fillrect(150, 40, 100, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.restore' in that specification...

CanvasRenderingContext2D.save() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // save the default state ctx.save(); ctx.fillstyle = 'green'; ctx.fillrect(10, 10, 100, 100); // restore the default state ctx.restore(); ctx.fillrect(150, 40, 100, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.save' in that specification.

CanvasRenderingContext2D.setTransform() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.settransform(1, .2, .8, 1, 0, 0); ctx.fillrect(0, 0, 100, 100); result retrieving and passing a dommatrix object in the following example, we have two <canvas> elements.

CanvasRenderingContext2D.shadowBlur - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // shadow ctx.shadowcolor = 'red'; ctx.shadowblur = 15; // rectangle ctx.fillstyle = 'blue'; ctx.fillrect(20, 20, 150, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.shadowblur' in that specification.

CanvasRenderingContext2D.shadowOffsetX - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // shadow ctx.shadowcolor = 'red'; ctx.shadowoffsetx = 25; ctx.shadowblur = 10; // rectangle ctx.fillstyle = 'blue'; ctx.fillrect(20, 20, 150, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.shadowoffsetx' in that specification.

CanvasRenderingContext2D.shadowOffsetY - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // shadow ctx.shadowcolor = 'red'; ctx.shadowoffsety = 25; ctx.shadowblur = 10; // rectangle ctx.fillstyle = 'blue'; ctx.fillrect(20, 20, 150, 80); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.shadowoffsety' in that specification.

CanvasRenderingContext2D.textBaseline - Web APIs
html <canvas id="canvas" width="550" height="500"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); const baselines = ['top', 'hanging', 'middle', 'alphabetic', 'ideographic', 'bottom']; ctx.font = '36px serif'; ctx.strokestyle = 'red'; baselines.foreach(function (baseline, index) { ctx.textbaseline = baseline; const y = 75 + index * 75; ctx.beginpath(); ctx.moveto(0, y + 0.5); ctx.lineto(550, y + 0.5); ctx.stroke(); ctx.filltext('...

CanvasRenderingContext2D.transform() - Web APIs
html <canvas id="canvas"></canvas> javascript const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); ctx.transform(1, .2, .8, 1, 0, 0); ctx.fillrect(0, 0, 100, 100); result specifications specification status comment html living standardthe definition of 'canvasrenderingcontext2d.transform' in that specification.

CanvasRenderingContext2D.translate() - Web APIs
const canvas = document.getelementbyid('canvas'); const ctx = canvas.getcontext('2d'); // moved square ctx.translate(110, 30); ctx.fillstyle = 'red'; ctx.fillrect(0, 0, 80, 80); // reset current transformation matrix to the identity matrix ctx.settransform(1, 0, 0, 1, 0, 0); // unmoved square ctx.fillstyle = 'gray'; ctx.fillrect(0, 0, 80, 80); result the moved square is red, and the unmoved square is gray.

CanvasRenderingContext2D - Web APIs
basic example to get a canvasrenderingcontext2d instance, you must first have an html <canvas> element to work with: <canvas id="my-house" width="300" height="300"></canvas> to get the canvas' 2d rendering context, call getcontext() on the <canvas> element, supplying '2d' as the argument: const canvas = document.getelementbyid('my-house'); const ctx = canvas.getcontext('2d'); with the context in hand, you can draw anything you like.

Manipulating video using canvas - Web APIs
var processor; processor.doload = function doload() { this.video = document.getelementbyid('video'); this.c1 = document.getelementbyid('c1'); this.ctx1 = this.c1.getcontext('2d'); this.c2 = document.getelementbyid('c2'); this.ctx2 = this.c2.getcontext('2d'); let self = this; this.video.addeventlistener('play', function() { self.width = self.video.videowidth / 2; self.height = self.video.videoheight / 2; self.timercallback(); }, fals...

Compositing and clipping - Web APIs
function draw() { var ctx = document.getelementbyid('canvas').getcontext('2d'); ctx.fillrect(0, 0, 150, 150); ctx.translate(75, 75); // create a circular clipping path ctx.beginpath(); ctx.arc(0, 0, 60, 0, math.pi * 2, true); ctx.clip(); // draw background var lingrad = ctx.createlineargradient(0, -75, 0, 75); lingrad.addcolorstop(0, '#232256'); lingrad.addcolorstop(1, '#143778'); ctx.fillstyle = lingrad; ctx.fillrect(-7...

Hit regions and accessibility - Web APIs
<canvas id="canvas"></canvas> <script> var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.arc(70, 80, 10, 0, 2 * math.pi, false); ctx.fill(); ctx.addhitregion({id: 'circle'}); canvas.addeventlistener('mousemove', function(event) { if (event.region) { alert('hit region: ' + event.region); } }); </script> the addhitregion() method also takes a control option to route events to an element (that is a descendant ...

Using channel messaging - Web APIs
var input = document.getelementbyid('message-input'); var output = document.getelementbyid('message-output'); var button = document.queryselector('button'); var iframe = document.queryselector('iframe'); var channel = new messagechannel(); var port1 = channel.port1; // wait for the iframe to load iframe.addeventlistener("load", onload); function onload() { // listen for button clicks button.addeventlistener('click', onclick)...

ChildNode.remove() - Web APIs
syntax node.remove(); example using remove() <div id="div-01">here is div-01</div> <div id="div-02">here is div-02</div> <div id="div-03">here is div-03</div> var el = document.getelementbyid('div-02'); el.remove(); // removes the div with the 'div-02' id childnode.remove() is unscopable the remove() method is not scoped into the with statement.

Clipboard.readText() - Web APIs
navigator.clipboard.readtext().then( cliptext => document.getelementbyid("outbox").innertext = cliptext); specifications specification status comment clipboard api and eventsthe definition of 'readtext()' in that specification.

CustomElementRegistry.get() - Web APIs
examples customelements.define('my-paragraph', class extends htmlelement { constructor() { super(); let template = document.getelementbyid('my-paragraph'); let templatecontent = template.content; const shadowroot = this.attachshadow({mode: 'open'}) .appendchild(templatecontent.clonenode(true)); } }) // return a reference to the my-paragraph constructor let ctor = customelements.get('my-paragraph'); specifications specification status comment html living standardthe definition of 'cu...

CustomElementRegistry.whenDefined() - Web APIs
<menu-item>item n</menu-item> </nav-menu> </nav> const container = document.getelementbyid('menu-container'); const placeholder = container.queryselector('.menu-placeholder'); // fetch all the children of menu that are not yet defined.

DOMImplementation.createDocument() - Web APIs
example var doc = document.implementation.createdocument ('http://www.w3.org/1999/xhtml', 'html', null); var body = document.createelementns('http://www.w3.org/1999/xhtml', 'body'); body.setattribute('id', 'abc'); doc.documentelement.appendchild(body); alert(doc.getelementbyid('abc')); // [object htmlbodyelement] specifications specification status comment domthe definition of 'domimplementation.createdocument' in that specification.

DOMImplementation.createHTMLDocument() - Web APIs
here's the html for this example: <body> <p>click <a href="javascript:makedocument()">here</a> to create a new document and insert it below.</p> <iframe id="theframe" src="about:blank" /> </body> the javascript implementation of makedocument() follows: function makedocument() { let frame = document.getelementbyid("theframe"); let doc = document.implementation.createhtmldocument("new document"); let p = doc.createelement("p"); p.innerhtml = "this is a new paragraph."; try { doc.body.appendchild(p); } catch(e) { console.log(e); } // copy the new html document into the frame let destdocument = frame.contentdocument; let srcnode = doc.documentelement; let newnode = destdocument...

DOMMatrixReadOnly.flipX() - Web APIs
const flipped = document.getelementbyid('flipped'); const matrix = new dommatrixreadonly(); const flippedmatrix = matrix.flipx(); flipped.setattribute('transform', flippedmatrix.tostring()); screenshotlive sample specifications specification status comment geometry interfaces module level 1the definition of 'dommatrixreadonly.flipx()' in that specification.

DOMTokenList.supports() - Web APIs
example let iframe = document.getelementbyid('display'); if (iframe.sandbox.supports('an-upcoming-feature')) { // support code for mystery future feature } else { // fallback code } if (iframe.sandbox.supports('allow-scripts')) { // instruct frame to run javascript // // (note: this feature is well-supported; this is just an example!) // } specifications specification status comment credential man...

DataTransfer.dropEffect - Web APIs
a("text", ev.target.id); ev.datatransfer.effectallowed = "move"; } function drop_handler(ev) { console.log("drop: dropeffect = " + ev.datatransfer.dropeffect + " ; effectallowed = " + ev.datatransfer.effectallowed); ev.preventdefault(); // get the id of the target and add the moved element to the target's dom var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragover_handler(ev) { console.log("dragover: dropeffect = " + ev.datatransfer.dropeffect + " ; effectallowed = " + ev.datatransfer.effectallowed); ev.preventdefault(); // set the dropeffect to move ev.datatransfer.dropeffect = "move" } specifications specification status comment html living standardthe definition of 'dropeffect' in that sp...

DataTransfer.effectAllowed - Web APIs
.setdata("text", ev.target.id); ev.datatransfer.effectallowed = "move"; } function drop_handler(ev) { console.log("drop: dropeffect = " + ev.datatransfer.dropeffect + " ; effectallowed = " + ev.datatransfer.effectallowed); ev.preventdefault(); // get the id of the target and add the moved element to the target's dom var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragover_handler(ev) { console.log("dragover: dropeffect = " + ev.datatransfer.dropeffect + " ; effectallowed = " + ev.datatransfer.effectallowed); ev.preventdefault(); // set the dropeffect to move ev.datatransfer.dropeffect = "move" } </script> <body> <h1>examples <code>datatransfer</code>.{<code>dropeffect</code>, <code>effectallowed</code>} properties</h1> <div> <p...

DataTransfer.getData() - Web APIs
llowdropevent) { allowdropevent.target.style.color = 'blue'; allowdropevent.preventdefault(); } function drag(dragevent) { dragevent.datatransfer.setdata("text", dragevent.target.id); dragevent.target.style.color = 'green'; } function drop(dropevent) { dropevent.preventdefault(); var data = dropevent.datatransfer.getdata("text"); dropevent.target.appendchild(document.getelementbyid(data)); document.getelementbyid("drag").style.color = 'black'; } result specifications specification status comment html living standardthe definition of 'getdata()' in that specification.

DataTransfer.items - Web APIs
r will // know which element to add to its tree ev.datatransfer.setdata("text/plain", ev.target.id); ev.datatransfer.effectallowed = "move"; } function drop_handler(ev) { console.log("drop: target.id = " + ev.target.id); ev.preventdefault(); // get the id of the target and add the moved element to the target's dom var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); // print each format type if (ev.datatransfer.types != null) { for (var i=0; i < ev.datatransfer.types.length; i++) { console.log("...

DataTransfer.setData() - Web APIs
use the event target's id for the data ev.datatransfer.setdata("text/plain", ev.target.id); } function dragover_handler(ev) { console.log("dragover"); ev.preventdefault(); } function drop_handler(ev) { console.log("drop"); ev.preventdefault(); // get the data, which is the id of the drop target var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); // clear the drag data cache (for all formats/types) ev.datatransfer.cleardata(); } </script> <body> <h1>examples of <code>datatransfer</code>: <code>setdata()</code>, <code>getdata()</code>, <code>cleardata()</code></h1> <div> <p id="source" ondragstart="dragstart_handler(event);" draggable="true"> select this element, drag it to the drop zone and then release the selection to...

DataTransfer.setDragImage() - Web APIs
var img = new image(); img.src = 'example.gif'; ev.datatransfer.setdragimage(img, 10, 10); } function dragover_handler(ev) { console.log("dragover"); ev.preventdefault(); } function drop_handler(ev) { console.log("drop"); ev.preventdefault(); // get the data, which is the id of the drop target var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } </script> <body> <h1>example of <code>datatransfer.setdragimage()</code></h1> <div> <p id="source" ondragstart="dragstart_handler(event);" draggable="true"> select this element, drag it to the drop zone and then release the selection to move the element.</p> </div> <div id="target" ondrop="drop_handler(event);" ondragover="dragover_handler(event);">drop zone</div> </body> </h...

DataTransfer.types - Web APIs
r will // know which element to add to its tree ev.datatransfer.setdata("text/plain", ev.target.id); ev.datatransfer.effectallowed = "move"; } function drop_handler(ev) { console.log("drop: target.id = " + ev.target.id); ev.preventdefault(); // get the id of the target and add the moved element to the target's dom var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); // print each format type if (ev.datatransfer.types != null) { for (var i=0; i < ev.datatransfer.types.length; i++) { console.log("...

DataTransferItem.getAsFile() - Web APIs
function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = event.datatransfer.items; for (var i = 0; i < data.length; i += 1) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html console.log("...

DataTransferItem.getAsString() - Web APIs
function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.items; for (var i = 0; i < data.length; i += 1) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html console.log("...

DataTransferItem.kind - Web APIs
function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = event.datatransfer.items; for (var i = 0; i < data.length; i += 1) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html console.log("...

DataTransferItem.type - Web APIs
function drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.items; for (var i = 0; i < data.length; i += 1) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html console.log("...

DataTransferItem.webkitGetAsEntry() - Web APIs
let dropzone = document.getelementbyid("dropzone"); let listing = document.getelementbyid("listing"); function scanfiles(item, container) { let elem = document.createelement("li"); elem.innerhtml = item.name; container.appendchild(elem); if (item.isdirectory) { let directoryreader = item.createreader(); let directorycontainer = document.createelement("ul"); container.appendchild(directorycontainer); directoryr...

DataTransferItemList.DataTransferItem() - Web APIs
unction drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.items; // loop through the dropped items and log their data for (var i = 0; i < data.length; i++) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html data[i].getasstring(function (s){ console.log("...

DataTransferItemList.add() - Web APIs
tion drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = event.datatransfer.items; // loop through the dropped items and log their data for (var i = 0; i < data.length; i++) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html data[i].getasstring(function (s){ console.log("...

DataTransferItemList.clear() - Web APIs
tion drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = event.datatransfer.items; // loop through the dropped items and log their data for (var i = 0; i < data.length; i++) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html data[i].getasstring(function (s){ console.log("...

DataTransferItemList.length - Web APIs
unction drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = ev.datatransfer.items; // loop through the dropped items and log their data for (var i = 0; i < data.length; i++) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html data[i].getasstring(function (s){ console.log("...

DataTransferItemList.remove() - Web APIs
tion drop_handler(ev) { console.log("drop"); ev.preventdefault(); var data = event.datatransfer.items; // loop through the dropped items and log their data for (var i = 0; i < data.length; i++) { if ((data[i].kind == 'string') && (data[i].type.match('^text/plain'))) { // this item is the target node data[i].getasstring(function (s){ ev.target.appendchild(document.getelementbyid(s)); }); } else if ((data[i].kind == 'string') && (data[i].type.match('^text/html'))) { // drag data item is html data[i].getasstring(function (s){ console.log("...

Document.URL - Web APIs
syntax const url = document.url example javascript document.getelementbyid("url").textcontent = document.url; html <p id="urltext"> url:<br/> <span id="url">url goes here</span> </p> result specifications specification status comment domthe definition of 'document.url' in that specification.

Document.adoptNode() - Web APIs
example const iframe = document.queryselector('iframe'); const iframeimages = iframe.contentdocument.queryselectorall('img'); const newparent = document.getelementbyid('images'); iframeimages.foreach(function(imgel) { newparent.appendchild(document.adoptnode(imgel)); }); notes before they can be inserted into the current document, nodes from external documents should either be: cloned using document.importnode(); or adopted using document.adoptnode().

Document.anchors - Web APIs
example if (document.anchors.length >= 5) { dump("found too many anchors"); } the following is an example that auto populates a table of contents with every anchor on the page: <!doctype html> <html lang="en"> <head> <meta charset="utf-8" /> <title>test</title> <script> function init() { var toc = document.getelementbyid("toc"); var i, li, newanchor; for (i = 0; i < document.anchors.length; i++) { li = document.createelement("li"); newanchor = document.createelement('a'); newanchor.href = "#" + document.anchors[i].name; newanchor.innerhtml = document.anchors[i].text; li.appendchild(newanchor); toc.appendchild(li); } } </script> </head> <body onload="init()"> <h1>title</h1> <h2><a na...

Document.createAttribute() - Web APIs
example var node = document.getelementbyid("div1"); var a = document.createattribute("my_attrib"); a.value = "newval"; node.setattributenode(a); console.log(node.getattribute("my_attrib")); // "newval" specifications specification status comment domthe definition of 'document.createattribute()' in that specification.

Document.createDocumentFragment() - Web APIs
html <ul id="ul"> </ul> javascript var element = document.getelementbyid('ul'); // assuming ul exists var fragment = document.createdocumentfragment(); var browsers = ['firefox', 'chrome', 'opera', 'safari', 'internet explorer']; browsers.foreach(function(browser) { var li = document.createelement('li'); li.textcontent = browser; fragment.appendchild(li); }); element.appendchild(fragment); result specifications specification status ...

Document.createElement() - Web APIs
= addelement; function addelement () { // create a new div element const newdiv = document.createelement("div"); // and give it some content const newcontent = document.createtextnode("hi there and greetings!"); // add the text node to the newly created div newdiv.appendchild(newcontent); // add the newly created element and its content into the dom const currentdiv = document.getelementbyid("div1"); document.body.insertbefore(newdiv, currentdiv); } web component example the following example snippet is taken from our expanding-list-web-component example (see it live also).

Document.createElementNS() - Web APIs
rom two different namespaces within a single document: <?xml version="1.0"?> <page xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" xmlns:html="http://www.w3.org/1999/xhtml" title="||working with elements||" onload="init()"> <script type="application/javascript"><![cdata[ let container; let newdiv; let txtnode; function init(){ container = document.getelementbyid("containerbox"); newdiv = document.createelementns("http://www.w3.org/1999/xhtml", "div"); txtnode = document.createtextnode("this is text that was constructed dynamically with createelementns and createtextnode then inserted into the document using appendchild."); newdiv.appendchild(txtnode); container.appendchild(newdiv); } ]]></script> <vbox id="containerbox" flex="1"> <html:...

Document.createTextNode() - Web APIs
example <!doctype html> <html lang="en"> <head> <title>createtextnode example</title> <script> function addtextnode(text) { var newtext = document.createtextnode(text), p1 = document.getelementbyid("p1"); p1.appendchild(newtext); } </script> </head> <body> <button onclick="addtextnode('yes!

Document.createTouch() - Web APIs
var target = document.getelementbyid("target"); var touch1 = document.createtouch(window, target, 1, 15, 20, 35, 40); var touch2 = document.createtouch(window, target, 2, 25, 30, 45, 50); specifications specification status comment touch eventsthe definition of 'document.createtouch()' in that specification.

Document.createTouchList() - Web APIs
var target = document.getelementbyid("target"); // create some touch points var touch1 = document.createtouch(window, target, 1, 15, 20, 35, 40); var touch2 = document.createtouch(window, target, 2, 25, 30, 45, 50); // create an empty touchlist objects var list0 = document.createtouchlist(); // create a touchlist with only one touch object var list1 = document.createtouchlist(touch1); // create a list with two touch objects var ...

Document.documentURI - Web APIs
syntax const uri = document.documenturi example javascript document.getelementbyid("url").textcontent = document.documenturi; html <p id="urltext"> url:<br/> <span id="url">url goes here</span> </p> result specifications specification status comment domthe definition of 'documenturi' in that specification.

Document.getBoxObjectFor() - Web APIs
example var mydiv = document.getelementbyid("mydiv"), boxobj = document.getboxobjectfor (mydiv); alert ( "x:" + boxobj.x + ", y:" + boxobj.y + ", width:" + boxobj.width + ", height:" + boxobj.height ); notes specified in nsixuldocument.idl ...

Document.getElementsByTagName() - Web APIs
<!doctype html> <html lang="en"> <head> <meta charset="utf-8" /> <title>getelementsbytagname example</title> <script> function getallparaelems() { var allparas = document.getelementsbytagname('p'); var num = allparas.length; alert('there are ' + num + ' paragraph in this document'); } function div1paraelems() { var div1 = document.getelementbyid('div1'); var div1paras = div1.getelementsbytagname('p'); var num = div1paras.length; alert('there are ' + num + ' paragraph in #div1'); } function div2paraelems() { var div2 = document.getelementbyid('div2'); var div2paras = div2.getelementsbytagname('p'); var num = div2paras.length; alert('there are ' + num + ' paragraph in #div2'); } </sc...

Document.getElementsByTagNameNS() - Web APIs
tml xmlns="http://www.w3.org/1999/xhtml"> <head> <title>getelementsbytagnamens example</title> <script type="text/javascript"> function getallparaelems() { var allparas = document.getelementsbytagnamens("http://www.w3.org/1999/xhtml", "p"); var num = allparas.length; alert("there are " + num + " &lt;p&gt; elements in this document"); } function div1paraelems() { var div1 = document.getelementbyid("div1") var div1paras = div1.getelementsbytagnamens("http://www.w3.org/1999/xhtml", "p"); var num = div1paras.length; alert("there are " + num + " &lt;p&gt; elements in div1 element"); } function div2paraelems() { var div2 = document.getelementbyid("div2") var div2paras = div2.getelementsbytagnamens("http://www.w3.org/1999/xhtml", "p"); var num = div2paras.length; alert("there...

Document.hasFocus() - Web APIs
html <p id="log">awaiting focus check.</p> <button onclick="openwindow()">open a new window</button> javascript function checkpagefocus() { let body = document.queryselector('body'); let log = document.getelementbyid('log'); if (document.hasfocus()) { log.textcontent = 'this document has the focus.'; body.style.background = '#fff'; } else { log.textcontent = 'this document does not have the focus.'; body.style.background = '#ccc'; } } function openwindow() { window.open('https://developer.mozilla.org/', 'mdn', 'width=640,height=320,left=150,top=150'); } // check page focus every 3...

Document.importNode() - Web APIs
example const iframe = document.queryselector("iframe"); const oldnode = iframe.contentwindow.document.getelementbyid("mynode"); const newnode = document.importnode(oldnode, true); document.getelementbyid("container").appendchild(newnode); notes before they can be inserted into the current document, nodes from external documents should either be: cloned using document.importnode(); or adopted using document.adoptnode().

Document: keypress event - Web APIs
<p>press inside this iframe first to focus it, then try pressing keys on the keyboard.</p> <p id="log"></p> const log = document.getelementbyid('log'); document.addeventlistener('keypress', logkey); function logkey(e) { log.textcontent += ` ${e.code}`; } onkeypress equivalent document.onkeypress = logkey; specifications specification status ui events working draft ...

Document: keyup event - Web APIs
by clicking in it), then try pressing some keys.</p> <p id="log"></p> const log = document.getelementbyid('log'); document.addeventlistener('keyup', logkey); function logkey(e) { log.textcontent += ` ${e.code}`; } onkeyup equivalent document.onkeyup = logkey; specifications specification status ui events working draft ...

Document.styleSheetSets - Web APIs
example given an <ul> (list) element with the id "sheetlist", you can populate it with the names of all the available style sheet sets with code like this: let list = document.getelementbyid('sheetlist'); let sheets = document.stylesheetsets; list.innerhtml = ''; for (let i = 0; i < sheets.length; i++) { let item = document.createelement('li'); item.innerhtml = sheets[i]; list.appendchild(item); } notes the list of available style sheet sets is constructed by enumerating all the style sheets available for the document, in the order in which they're listed in the document.s...

Document - Web APIs
the document interface is extended with the parentnode interface: document.getelementbyid(string id) returns an object reference to the identified element.

DocumentOrShadowRoot.activeElement - Web APIs
morbi sed euismod diam.</textarea> </form> <p>active element id: <b id="output-element"></b></p> <p>selected text: <b id="output-text"></b></p> javascript function onmouseup(e) { const activetextarea = document.activeelement; const selection = activetextarea.value.substring( activetextarea.selectionstart, activetextarea.selectionend ); const outputelement = document.getelementbyid('output-element'); const outputtext = document.getelementbyid('output-text'); outputelement.innerhtml = activetextarea.id; outputtext.innerhtml = selection; } const textarea1 = document.getelementbyid('ta-example-one'); const textarea2 = document.getelementbyid('ta-example-two'); textarea1.addeventlistener('mouseup', onmouseup, false); textarea2.addeventlistener('mouseup', onmouseup, false...

DocumentOrShadowRoot.elementsFromPoint() - Web APIs
example html <div> <p>some text</p> </div> <p>elements at point 30, 20:</p> <div id="output"></div> javascript let output = document.getelementbyid("output"); if (document.elementsfrompoint) { let elements = document.elementsfrompoint(30, 20); for (var i = 0; i < elements.length; i++) { output.textcontent += elements[i].localname; if (i < elements.length - 1) { output.textcontent += " < "; } } } else { output.innerhtml = "<span style=\"color: red;\">" + "browser does not support <code>document.elementsfrompoint...

DocumentOrShadowRoot.nodeFromPoint() - Web APIs
examples html content <div> <p>some text</p> </div> <p>top node at point 30, 20:</p> <div id="output"></div> javascript content var output = document.getelementbyid("output"); if (document.nodefrompoint) { var node = document.nodefrompoint(30, 20); output.textcontent += node.localname; } else { output.innerhtml = "<span style=\"color: red;\">" + "browser does not support <code>document.nodefrompoint()</code>" + "</span>"; } specifications not part of any specification at present.

DocumentOrShadowRoot.nodesFromPoint() - Web APIs
example html content <div> <p>some text</p> </div> <p>nodes at point 30, 20:</p> <div id="output"></div> javascript content var output = document.getelementbyid("output"); if (document.nodesfrompoint) { var nodes = document.nodesfrompoint(30, 20); for(var i = 0; i < nodes.length; i++) { output.textcontent += nodes[i].localname; if (i < nodes.length - 1) { output.textcontent += " < "; } } } else { output.innerhtml = "<span style=\"color: red;\">" + "browser does not support <code>document.nodesfrompoint()</code>" + "</s...

How whitespace is handled by HTML, CSS, and in the DOM - Web APIs
var cur = first_child(document.getelementbyid("test")); while (cur) { if (data_of(cur.firstchild) == "this is the third paragraph.") { cur.classname = "magic"; cur.firstchild.textcontent = "this is the magic paragraph."; } cur = node_after(cur); } ...

EffectTiming.direction - Web APIs
examples in the forgotten key example, alice waves her arm up and down by passing her an alternate value for her direction property: // get alice's arm, and wave it up and down document.getelementbyid("alice_arm").animate([ { transform: 'rotate(10deg)' }, { transform: 'rotate(-40deg)' } ], { easing: 'steps(2, end)', iterations: infinity, direction: 'alternate', duration: 600 }); specifications specification status comment web animationsthe definition of 'direction' in that specification.

EffectTiming.easing - Web APIs
examples in the red queen's race example, we animate alice and the red queen by passing an easing of steps(7, end) to animate(): // define the key frames var spriteframes = [ { transform: 'translatey(0)' }, { transform: 'translatey(-100%)' } ]; // get the element that represents alice and the red queen var redqueen_alice_sprite = document.getelementbyid('red-queen_and_alice_sprite'); // animate alice and the red queen using steps() var redqueen_alice = redqueen_alice_sprite.animate( spriteframes, { easing: 'steps(7, end)', direction: "reverse", duration: 600, playbackrate: 1, iterations: infinity }); specifications specification status comment web animationsthe definition of 'easing' in that specification.

EffectTiming.fill - Web APIs
document.getelementbyid("animatebutton").addeventlistener("click", event => { document.getelementbyid("box").animate( boxrotationkeyframes, boxrotationtiming ); }, false); the rest of the code is pretty simple: it adds an event listener to the "animate" button so that when it's clicked by the user, the box is animated by calling element.animate() on it, providing the boxrotationkeyframes and boxrotationtimi...

EffectTiming.iterations - Web APIs
examples in the forgotten key example, alice waves her arm up and down the entire time the page is open by passing infinity as the value for her iterations property: // get alice's arm, and wave it up and down document.getelementbyid("alice_arm").animate([ { transform: 'rotate(10deg)' }, { transform: 'rotate(-40deg)' } ], { easing: 'steps(2, end)', iterations: infinity, direction: 'alternate', duration: 600 }); specifications specification status comment web animationsthe definition of 'iterations' in that specification.

Element.animate() - Web APIs
document.getelementbyid("tunnel").animate([ // keyframes { transform: 'translatey(0px)' }, { transform: 'translatey(-300px)' } ], { // timing options duration: 1000, iterations: infinity }); implicit to/from keyframes in newer browser versions, you are able to set a beginning or end state for an animation only (i.e.

Element.attributes - Web APIs
<!doctype html> <html> <head> <title>attributes example</title> <script type="text/javascript"> function listattributes() { var paragraph = document.getelementbyid("paragraph"); var result = document.getelementbyid("result"); // first, let's verify that the paragraph has some attributes if (paragraph.hasattributes()) { var attrs = paragraph.attributes; var output = ""; for(var i = attrs.length - 1; i >= 0; i--) { output += attrs[i].name + "->" + attrs[i].value; } result.value = output; } else ...

Element: blur event - Web APIs
html <form id="form"> <input type="text" placeholder="text input"> <input type="password" placeholder="password"> </form> javascript const form = document.getelementbyid('form'); form.addeventlistener('focus', (event) => { event.target.style.background = 'pink'; }, true); form.addeventlistener('blur', (event) => { event.target.style.background = ''; }, true); result specifications specification status comment ui events working draft added info that this event is composed.

Element.className - Web APIs
example let el = document.getelementbyid('item'); if (el.classname === 'active'){ el.classname = 'inactive'; } else { el.classname = 'active'; } notes the name classname is used for this property instead of class because of conflicts with the "class" keyword in many languages which are used to manipulate the dom.

Element.closest() - Web APIs
example html <article> <div id="div-01">here is div-01 <div id="div-02">here is div-02 <div id="div-03">here is div-03</div> </div> </div> </article> javascript var el = document.getelementbyid('div-03'); var r1 = el.closest("#div-02"); // returns the element with the id=div-02 var r2 = el.closest("div div"); // returns the closest ancestor which is a div in div, here it is the div-03 itself var r3 = el.closest("article > div"); // returns the closest ancestor which is a div and has a parent article, here it is the div-01 var r4 = el.closest(":not(div)"); // returns the closest ance...

Element: contextmenu event - Web APIs
html <p id="nocontextmenu">the context menu has been disabled on this paragraph.</p> <p>but it has not been disabled on this one.</p> javascript nocontext = document.getelementbyid('nocontextmenu'); nocontext.addeventlistener('contextmenu', e => { e.preventdefault(); }); result specifications specification status comment html living standardthe definition of 'contextmenu' in that specification.

Element: focus event - Web APIs
html <form id="form"> <input type="text" placeholder="text input"> <input type="password" placeholder="password"> </form> javascript const form = document.getelementbyid('form'); form.addeventlistener('focus', (event) => { event.target.style.background = 'pink'; }, true); form.addeventlistener('blur', (event) => { event.target.style.background = ''; }, true); result specifications specification status comment ui events working draft added info that this event is composed.

Element: focusin event - Web APIs
bubbles yes cancelable no interface focusevent event handler property onfocusin sync / async sync composed yes examples live example html <form id="form"> <input type="text" placeholder="text input"> <input type="password" placeholder="password"> </form> javascript const form = document.getelementbyid('form'); form.addeventlistener('focusin', (event) => { event.target.style.background = 'pink'; }); form.addeventlistener('focusout', (event) => { event.target.style.background = ''; }); result specifications specification status comment ui events working draft added info that this event is composed.

Element: focusout event - Web APIs
bubbles yes cancelable no interface focusevent event handler property onfocusout sync / async sync composed yes examples live example html <form id="form"> <input type="text" placeholder="text input"> <input type="password" placeholder="password"> </form> javascript const form = document.getelementbyid('form'); form.addeventlistener('focusin', (event) => { event.target.style.background = 'pink'; }); form.addeventlistener('focusout', (event) => { event.target.style.background = ''; }); result specifications specification status comment ui events working draft added info that this event is composed.

Element.getAttribute() - Web APIs
examples const div1 = document.getelementbyid('div1'); const align = div1.getattribute('align'); alert(align); // shows the value of align for the element with id="div1" description lower casing when called on an html element in a dom flagged as an html document, getattribute() lower-cases its argument before proceeding.

Element.getAttributeNode() - Web APIs
example // html: <div id="top" /> let t = document.getelementbyid("top"); let idattr = t.getattributenode("id"); alert(idattr.value == "top") notes when called on an html element in a dom flagged as an html document, getattributenode lower-cases its argument before proceeding.

Element.getAttributeNodeNS() - Web APIs
== example == tbd the example needs to be fixed pre> // html: <div id="top" /> t = document.getelementbyid("top"); specialnode = t.getattributenodens( "http://www.mozilla.org/ns/specialspace", "id"); // inode.value = "full-top" </pre notes getattributenodens is more specific than getattributenode in that it allows you to specify attributes that are part of a particular namespace.

Element.getElementsByClassName() - Web APIs
examples matching a single class to look for elements that include among their classes a single specified class, we just provide that class name when calling getelementsbyclassname(): element.getelementsbyclassname('test'); this example finds all elements that have a class of test, which are also a descendant of the element that has the id of main: document.getelementbyid('main').getelementsbyclassname('test'); matching multiple classes to find elements whose class lists include both the red and test classes: element.getelementsbyclassname('red test'); examining the results you can use either the item() method on the returned htmlcollection or standard array syntax to examine individual elements in the collection.

Element.getElementsByTagName() - Web APIs
example // check the status of each data cell in a table const table = document.getelementbyid('forecast-table'); const cells = table.getelementsbytagname('td'); for (let cell of cells) { let status = cell.getattribute('data-status'); if (status === 'open') { // grab the data } } specifications specification status comment domthe definition of 'element.getelementsbytagname()' in that specification.

Element.getElementsByTagNameNS() - Web APIs
var table = document.getelementbyid("forecast-table"); var cells = table.getelementsbytagnamens("http://www.w3.org/1999/xhtml", "td"); for (var i = 0; i < cells.length; i++) { var axis = cells[i].getattribute("axis"); if (axis == "year") { // grab the data } } specifications specification status comment domthe definition of 'element.getelementsbytagnamens()' in that specification.

Element.hasAttribute() - Web APIs
example var foo = document.getelementbyid("foo"); if (foo.hasattribute("bar")) { // do something } polyfill ;(function(prototype) { prototype.hasattribute = prototype.hasattribute || function(name) { return !!(this.attributes[name] && this.attributes[name].specified); } })(element.prototype); notes dom methods dealing with element's attributes: not namespace-aware, most commonly used methods namespace-aware variants (dom level 2) dom level 1 methods for dealing wit...

Element.hasAttributeNS() - Web APIs
example // check that the attribute exists before you set a value var d = document.getelementbyid("div1"); if (d.hasattributens( "http://www.mozilla.org/ns/specialspace/", "special-align")) { d.setattribute("align", "center"); } notes dom methods dealing with element's attributes: not namespace-aware, most commonly used methods namespace-aware variants (dom level 2) dom level 1 methods for dealing with attr nodes directly (seldom used) dom level 2 namespace-aware methods...

Element.hasAttributes() - Web APIs
examples let foo = document.getelementbyid('foo'); if (foo.hasattributes()) { // do something with 'foo.attributes' } polyfill ;(function(prototype) { prototype.hasattributes = prototype.hasattributes || function() { return (this.attributes.length > 0); } })(element.prototype); specifications specification status comment domthe definition of 'element.hasattributes()' in that specification.

Element.id - Web APIs
the id is often used with getelementbyid() to retrieve a particular element.

Element.insertAdjacentHTML() - Web APIs
example // <div id="one">one</div> var d1 = document.getelementbyid('one'); d1.insertadjacenthtml('afterend', '<div id="two">two</div>'); // at this point, the new structure is: // <div id="one">one</div><div id="two">two</div> notes security considerations when inserting html into a page by using insertadjacenthtml(), be careful not to use user input that hasn't been escaped.

Element: keydown event - Web APIs
<input placeholder="click here, then press down a key." size="40"> <p id="log"></p> const input = document.queryselector('input'); const log = document.getelementbyid('log'); input.addeventlistener('keydown', logkey); function logkey(e) { log.textcontent += ` ${e.code}`; } onkeydown equivalent input.onkeydown = logkey; specifications specification status ui events working draft ...

Element: keypress event - Web APIs
<div> <label for="sample">focus the input and type something:</label> <input type="text" name="text" id="sample"> </div> <p id="log"></p> const log = document.getelementbyid('log'); const input = document.queryselector('input'); input.addeventlistener('keypress', logkey); function logkey(e) { log.textcontent += ` ${e.code}`; } onkeypress equivalent input.onkeypress = logkey; specifications specification status ui events working draft ...

Element: keyup event - Web APIs
<input placeholder="click here, then press and release a key." size="40"> <p id="log"></p> const input = document.queryselector('input'); const log = document.getelementbyid('log'); input.addeventlistener('keyup', logkey); function logkey(e) { log.textcontent += ` ${e.code}`; } onkeyup equivalent input.onkeyup = logkey; specifications specification status ui events working draft ...

Element.localName - Web APIs
example (must be served with xml content type, such as text/xml or application/xhtml+xml.) <html xmlns="http://www.w3.org/1999/xhtml" xmlns:svg="http://www.w3.org/2000/svg"> <head> <script type="application/javascript"><![cdata[ function test() { var text = document.getelementbyid('text'); var circle = document.getelementbyid('circle'); text.value = "<svg:circle> has:\n" + "localname = '" + circle.localname + "'\n" + "namespaceuri = '" + circle.namespaceuri + "'"; } ]]></script> </head> <body onload="test()"> <svg:svg version="1.1" width="100px" height="100px" viewbox="0 0 100 100"> <svg:circle cx="50" cy="50" r=...

Element: mousedown event - Web APIs
html <h1>drawing with mouse events</h1> <canvas id="mypics" width="560" height="360"></canvas> css canvas { border: 1px solid black; width: 560px; height: 360px; } javascript // when true, moving the mouse draws on the canvas let isdrawing = false; let x = 0; let y = 0; const mypics = document.getelementbyid('mypics'); const context = mypics.getcontext('2d'); // event.offsetx, event.offsety gives the (x,y) offset from the edge of the canvas.

Element: mouseenter event - Web APIs
#mousetarget { box-sizing: border-box; width:15rem; border:1px solid #333; } javascript var entereventcount = 0; var leaveeventcount = 0; const mousetarget = document.getelementbyid('mousetarget'); const unorderedlist = document.getelementbyid('unorderedlist'); mousetarget.addeventlistener('mouseenter', e => { mousetarget.style.border = '5px dotted orange'; entereventcount++; addlistitem('this is mouseenter event ' + entereventcount + '.'); }); mousetarget.addeventlistener('mouseleave', e => { mousetarget.style.border = '1px solid #333'; leaveeventcount++; addl...

Element: mouseleave event - Web APIs
#mousetarget { box-sizing: border-box; width:15rem; border:1px solid #333; } javascript var entereventcount = 0; var leaveeventcount = 0; const mousetarget = document.getelementbyid('mousetarget'); const unorderedlist = document.getelementbyid('unorderedlist'); mousetarget.addeventlistener('mouseenter', e => { mousetarget.style.border = '5px dotted orange'; entereventcount++; addlistitem('this is mouseenter event ' + entereventcount + '.'); }); mousetarget.addeventlistener('mouseleave', e => { mousetarget.style.border = '1px solid #333'; leaveeventcount++; addl...

Element: mousemove event - Web APIs
html <h1>drawing with mouse events</h1> <canvas id="mypics" width="560" height="360"></canvas> css canvas { border: 1px solid black; width: 560px; height: 360px; } javascript // when true, moving the mouse draws on the canvas let isdrawing = false; let x = 0; let y = 0; const mypics = document.getelementbyid('mypics'); const context = mypics.getcontext('2d'); // event.offsetx, event.offsety gives the (x,y) offset from the edge of the canvas.

Element: mouseout event - Web APIs
html <ul id="test"> <li>item 1</li> <li>item 2</li> <li>item 3</li> </ul> javascript let test = document.getelementbyid("test"); // briefly make the list purple when the mouse moves off the // <ul> element test.addeventlistener("mouseleave", function( event ) { // highlight the mouseleave target event.target.style.color = "purple"; // reset the color after a short delay settimeout(function() { event.target.style.color = ""; }, 1000); }, false); // briefly make an <li> orange when the mouse moves o...

Element: mouseover event - Web APIs
html <ul id="test"> <li>item 1</li> <li>item 2</li> <li>item 3</li> </ul> javascript let test = document.getelementbyid("test"); // this handler will be executed only once when the cursor // moves over the unordered list test.addeventlistener("mouseenter", function( event ) { // highlight the mouseenter target event.target.style.color = "purple"; // reset the color after a short delay settimeout(function() { event.target.style.color = ""; }, 500); }, false); // this handler will be executed every ...

Element: mouseup event - Web APIs
html <h1>drawing with mouse events</h1> <canvas id="mypics" width="560" height="360"></canvas> css canvas { border: 1px solid black; width: 560px; height: 360px; } javascript // when true, moving the mouse draws on the canvas let isdrawing = false; let x = 0; let y = 0; const mypics = document.getelementbyid('mypics'); const context = mypics.getcontext('2d'); // event.offsetx, event.offsety gives the (x,y) offset from the edge of the canvas.

Element.outerHTML - Web APIs
examples getting the value of an element's outerhtml property: html <div id="d"> <p>content</p> <p>further elaborated</p> </div> javascript var d = document.getelementbyid("d"); console.log(d.outerhtml); // the string '<div id="d"><p>content</p><p>further elaborated</p></div>' // is written to the console window replacing a node by setting the outerhtml property: html <div id="container"> <div id="d">this is a div.</div> </div> javascript var container = document.getelementbyid("container"); var d = document.getelementbyid("d"); console.log(container.firs...

Element: overflow event - Web APIs
les <div id="wrapper"> <div id="child"></div> </div> <br/> <label><input type="checkbox" id="toggle" checked/> overflow</label> <style> #wrapper { width: 20px; height: 20px; background: #000; padding: 5px; overflow: hidden; } #child { width: 40px; height: 40px; border: 2px solid grey; background: #ccc; } </style> <script> var wrapper = document.getelementbyid("wrapper"), child = document.getelementbyid("child"), toggle = document.getelementbyid("toggle"); wrapper.addeventlistener("overflow", function( event ) { console.log( event ); }, false); wrapper.addeventlistener("underflow", function( event ) { console.log( event ); }, false); toggle.addeventlistener("change", function( event ) { if ( event.target.check...

Element.querySelector() - Web APIs
html <div> <h5>original content</h5> <p> inside paragraph <span>inside span</span> inside paragraph </p> </div> <div> <h5>output</h5> <div id="output"></div> </div> javascript var baseelement = document.queryselector("p"); document.getelementbyid("output").innerhtml = (baseelement.queryselector("div span").innerhtml); result the result looks like this: notice how the "div span" selector still successfully matches the <span> element, even though the baseelement's child nodes do not include the div element (it is still part of the specified selector).

Element.releasePointerCapture() - Web APIs
align-items: center; justify-content: center; background: #fbe; } javascript function beginsliding(e) { slider.onpointermove = slide; slider.setpointercapture(e.pointerid); } function stopsliding(e) { slider.onpointermove = null; slider.releasepointercapture(e.pointerid); } function slide(e) { slider.style.transform = `translate(${e.clientx - 70}px)`; } const slider = document.getelementbyid('slider'); slider.onpointerdown = beginsliding; slider.onpointerup = stopsliding; result specifications specification status comment pointer events – level 2the definition of 'releasepointercapture' in that specification.

Element.removeAttribute() - Web APIs
e-aware methods for dealing with attr nodes directly (seldom used) setattribute (dom 1) setattributens setattributenode setattributenodens getattribute (dom 1) getattributens getattributenode getattributenodens hasattribute (dom 2) hasattributens - - removeattribute (dom 1) removeattributens removeattributenode - example // given: <div id="div1" align="left" width="200px"> document.getelementbyid("div1").removeattribute("align"); // now: <div id="div1" width="200px"> specifications specification status comment domthe definition of 'element" removeattribute' in that specification.

Element.removeAttributeNS() - Web APIs
example // given: // <div id="div1" xmlns:special="http://www.mozilla.org/ns/specialspace" // special:specialalign="utterleft" width="200px" /> d = document.getelementbyid("div1"); d.removeattributens("http://www.mozilla.org/ns/specialspace", "specialalign"); // now: <div id="div1" width="200px" /> notes dom methods dealing with element's attributes: not namespace-aware, most commonly used methods namespace-aware variants (dom level 2) dom level 1 methods for dealing with attr nodes directly (seldom used) dom level 2 namespace-aware methods for dealing with a...

Element.removeAttributeNode() - Web APIs
example // given: <div id="top" align="center" /> var d = document.getelementbyid("top"); var d_align = d.getattributenode("align"); d.removeattributenode(d_align); // align is now removed: <div id="top" /> notes if the removed attribute has a default value, it is immediately replaced.

Element.scrollIntoView() - Web APIs
example var element = document.getelementbyid("box"); element.scrollintoview(); element.scrollintoview(false); element.scrollintoview({block: "end"}); element.scrollintoview({behavior: "smooth", block: "end", inline: "nearest"}); notes the element may not be scrolled completely to the top or bottom depending on the layout of other elements.

Element.scrollIntoViewIfNeeded() - Web APIs
example var element = document.getelementbyid("my-el"); element.scrollintoviewifneeded(); element.scrollintoviewifneeded(true); // centers the element in the visible area specifications not part of any specification.

Element.scrollLeft - Web APIs
example html <div id="container"> <div id="content">click the button to slide right!</div> </div> <button id="slide" type="button">slide right</button> css #container { width: 100px; height: 100px; border: 1px solid #ccc; overflow-x: scroll; } #content { width: 250px; background-color: #ccc; } javascript const button = document.getelementbyid('slide'); button.onclick = function () { document.getelementbyid('container').scrollleft += 20; }; result specifications specification status comment css object model (cssom) view modulethe definition of 'scrollleft' in that specification.

Element.scrollWidth - Web APIs
margin-bottom: 2em; } </style> </head> <body> <div id="adiv"> foobar-foobar-foobar-foobar </div> <button id="abutton"> check for overflow </button> <div id="anotherdiv"> foobar-foobar-foobar-foobar </div> <button id="anotherbutton"> check for overflow </button> </body> <script> var buttonone = document.getelementbyid('abutton'), buttontwo = document.getelementbyid('anotherbutton'), divone = document.getelementbyid('adiv'), divtwo = document.getelementbyid('anotherdiv'); //check to determine if an overflow is happening function isoverflowing(element) { return (element.scrollwidth > element.offsetwidth); } function alertoverflow(element) { if (isoverflowing(element)...

Element: select event - Web APIs
examples selection logger <input value="try selecting some text in this element."> <p id="log"></p> function logselection(event) { const log = document.getelementbyid('log'); const selection = event.target.value.substring(event.target.selectionstart, event.target.selectionend); log.textcontent = `you selected: ${selection}`; } const input = document.queryselector('input'); input.addeventlistener('select', logselection); onselect equivalent you can also set up the event handler using the onselect property: input.onselect = logselection; specification...

Element.setAttributeNS() - Web APIs
example let d = document.getelementbyid('d1'); d.setattributens('http://www.mozilla.org/ns/specialspace', 'spec:align', 'center'); notes dom methods dealing with element's attributes: not namespace-aware, most commonly used methods namespace-aware variants (dom level 2) dom level 1 methods for dealing with attr nodes directly (seldom used) dom level 2 namespace-aware methods for dealing with attr nodes directly (seldom used) ...

Element.setAttributeNode() - Web APIs
html <div id="one" align="left">one</div> <div id="two">two</div> javascript let d1 = document.getelementbyid('one'); let d2 = document.getelementbyid('two'); let a = d1.getattributenode('align'); d2.setattributenode(a.clonenode(true)); // returns: 'left' alert(d2.attributes[1].value); notes if the attribute named already exists on the element, that attribute is replaced with the new one and the replaced one is returned.

Element.setAttributeNodeNS() - Web APIs
example // <div id="one" xmlns:myns="http://www.mozilla.org/ns/specialspace" // myns:special-align="utterleft">one</div> // <div id="two">two</div> var myns = "http://www.mozilla.org/ns/specialspace"; var d1 = document.getelementbyid("one"); var d2 = document.getelementbyid("two"); var a = d1.getattributenodens(myns, "special-align"); d2.setattributenodens(a.clonenode(true)); alert(d2.attributes[1].value) // returns: `utterleft' notes if the specified attribute already exists on the element, then that attribute is replaced with the new one and the replaced one is returned.

Element.setPointerCapture() - Web APIs
align-items: center; justify-content: center; background: #fbe; } javascript function beginsliding(e) { slider.onpointermove = slide; slider.setpointercapture(e.pointerid); } function stopsliding(e) { slider.onpointermove = null; slider.releasepointercapture(e.pointerid); } function slide(e) { slider.style.transform = `translate(${e.clientx - 70}px)`; } const slider = document.getelementbyid('slider'); slider.onpointerdown = beginsliding; slider.onpointerup = stopsliding; result specifications specification status comment pointer events – level 2the definition of 'setpointercapture' in that specification.

Element: show event - Web APIs
bubbles no cancelable no interface event event handler property onshow examples <div contextmenu="test"></div> <menu type="context" id="test"> <menuitem label="alert" onclick="alert('the alert label has been clicked')" /> </menu> <script> document.getelementbyid("test").addeventlistener("show", function(e){ alert("the context menu will be displayed"); }, false); </script> specifications specification status html5the definition of 'show event' in that specification.

Element.tagName - Web APIs
example html <span id="born">when i was born...</span> javascript var span = document.getelementbyid("born"); console.log(span.tagname); in xhtml (or any other xml format), the original case will be maintained, so "span" would be output in case the original tag name was created lowercase.

Element: underflow event - Web APIs
les <div id="wrapper"> <div id="child"></div> </div> <br/> <label><input type="checkbox" id="toggle" checked/> overflow</label> <style> #wrapper { width: 20px; height: 20px; background: #000; padding: 5px; overflow: hidden; } #child { width: 40px; height: 40px; border: 2px solid grey; background: #ccc; } </style> <script> var wrapper = document.getelementbyid("wrapper"), child = document.getelementbyid("child"), toggle = document.getelementbyid("toggle"); wrapper.addeventlistener("overflow", function( event ) { console.log( event ); }, false); wrapper.addeventlistener("underflow", function( event ) { console.log( event ); }, false); toggle.addeventlistener("change", function( event ) { if ( event.target.check...

ElementCSSInlineStyle.style - Web APIs
the following code snippet demonstrates the difference between the values obtained using the element's style property and that obtained using the getcomputedstyle() method: <!doctype html> <html> <body style="font-weight:bold;"> <div style="color:red" id="myelement">..</div> </body> </html> var element = document.getelementbyid("myelement"); var out = ""; var elementstyle = element.style; var computedstyle = window.getcomputedstyle(element, null); for (prop in elementstyle) { if (elementstyle.hasownproperty(prop)) { out += " " + prop + " = '" + elementstyle[prop] + "' > '" + computedstyle[prop] + "'\n"; } } console.log(out) the output would be something like: ...

Event.defaultPrevented - Web APIs
html <p><a id="link1" href="#link1">visit link 1</a></p> <p><a id="link2" href="#link2">try to visit link 2</a> (you can't)</p> <p id="log"></p> javascript function stoplink(event) { event.preventdefault(); } function logclick(event) { const log = document.getelementbyid('log'); if (event.target.tagname === 'a') { if (event.defaultprevented) { log.innertext = 'sorry, but you cannot visit this link!\n' + log.innertext; } else { log.innertext = 'visiting link...\n' + log.innertext; } } } const a = document.getelementbyid('link2'); a.addeventlistener('click', stoplink); document.addeventlistener('click', logclick); result specif...

Event.eventPhase - Web APIs
d3 <div id="d4">d4</div> </div> </div> </div> <div id="divinfo"></div> css div { margin: 20px; padding: 4px; border: thin black solid; } #divinfo { margin: 18px; padding: 8px; background-color:white; font-size:80%; } javascript let clear = false, divinfo = null, divs = null, usecapture = false; window.onload = function () { divinfo = document.getelementbyid('divinfo') divs = document.getelementsbytagname('div') chcapture = document.getelementbyid('chcapture') chcapture.onclick = function () { removelisteners() addlisteners() } clear() addlisteners() } function removelisteners() { for (let i = 0; i < divs.length; i++) { let d = divs[i] if (d.id != "divinfo") { d.removeeventlistener("click", ondivclick, true) ...

Event.msConvertURL() - Web APIs
example var bloblist = []; document.getelementbyid("pastezone").addeventlistener('paste', handlepaste, false); function handlepaste(evt) { var filelist = window.clipboarddata.files; // note that window.datatransfer.files is not applicable.

Event.timeStamp - Web APIs
</p> <p>timestamp: <span id="time">-</span></p> javascript function gettime(event) { var time = document.getelementbyid("time"); time.firstchild.nodevalue = event.timestamp; } document.body.addeventlistener("keypress", gettime); result reduced time precision to offer protection against timing attacks and fingerprinting, the precision of event.timestamp might get rounded depending on browser settings.

Event.type - Web APIs
html <p>press any key or click the mouse to get the event type.</p> <p id="log"></p> javascript function geteventtype(event) { const log = document.getelementbyid('log'); log.innertext = event.type + '\n' + log.innertext; } // keyboard events document.addeventlistener('keydown', geteventtype, false); // first document.addeventlistener('keypress', geteventtype, false); // second document.addeventlistener('keyup', geteventtype, false); // third // mouse events document.addeventlistener('mousedown', geteventtype, false); // first document.addeventlist...

EventListener - Web APIs
example html <button id="btn">click here!</button> javascript const buttonelement = document.getelementbyid('btn'); // add a handler for the 'click' event by providing a callback function.

EventTarget.removeEventListener() - Web APIs
const body = document.queryselector('body') const clicktarget = document.getelementbyid('click-target') const mouseovertarget = document.getelementbyid('mouse-over-target') let toggle = false; function makebackgroundyellow() { if (toggle) { body.style.backgroundcolor = 'white'; } else { body.style.backgroundcolor = 'yellow'; } toggle = !toggle; } clicktarget.addeventlistener('click', makebackgroundyellow, false ); mouseovertarget.addeventl...

Using Fetch - Web APIs
request bodies can be set by passing body parameters: const form = new formdata(document.getelementbyid('login-form')); fetch('/login', { method: 'post', body: form }); both request and response (and by extension the fetch() function), will try to intelligently determine the content type.

File.getAsBinary() - Web APIs
example // fileinput is an htmlinputelement: <input type="file" id="myfileinput" multiple> var fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (similar to nodelist) var files = fileinput.files; // object for allowed media types var accept = { binary : ["image/png", "image/jpeg"], text : ["text/plain", "text/css", "application/xml", "text/html"] }; var file; for (var i = 0; i < files.length; i++) { file = files[i]; // if file type could be detected if (file !== null) { if...

File.getAsDataURL() - Web APIs
syntax var url = instanceoffile.getasdataurl(); returns a string representing a data: url example // fileinput is a htmlinputelement: <input type="file" id="myfileinput" multiple> var fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (similar to nodelist) var files = fileinput.files; // array with acceptable file types var accept = ["image/png"]; // img is a htmlimgelement: <img id="myimg"> var img = document.getelementbyid("myimg"); // if we accept the first selected file type if (accept.indexof(files[0].mediatype) > -1) { // display the image // same as <img src="data:im...

File.getAsText() - Web APIs
example // fileinput is a htmlinputelement: <input type="file" id="myfileinput" multiple> var fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (similar to nodelist) var files = fileinput.files; // object for allowed media types var accept = { binary : ["image/png", "image/jpeg"], text : ["text/plain", "text/css", "application/xml", "text/html"] }; var file; for (var i = 0; i < files.length; i++) { file = files[i]; // if file type could be detected if (file !== null) { if...

File.lastModifiedDate - Web APIs
example // fileinput is a htmlinputelement: <input type="file" multiple id="myfileinput"> var fileinput = document.getelementbyid("myfileinput"); // files is a filelist object (simliar to nodelist) var files = fileinput.files; for (var i = 0; i < files.length; i++) { alert(files[i].name + " has a last modified date of " + files[i].lastmodifieddate); } reduced time precision to offer protection against timing attacks and fingerprinting, the precision of somefile.lastmodifieddate.gettime() might get rounded depending on...

File.webkitRelativePath - Web APIs
html content <input type="file" id="filepicker" name="filelist" webkitdirectory multiple /> <ul id="listing"></ul> javascript content document.getelementbyid("filepicker").addeventlistener("change", function(event) { let output = document.getelementbyid("listing"); let files = event.target.files; for (let i=0; i<files.length; i++) { let item = document.createelement("li"); item.innerhtml = files[i].webkitrelativepath; output.appendchild(item); }; }, false); result specifications specification status comment ...

FileSystemDirectoryReader.readEntries() - Web APIs
let dropzone = document.getelementbyid("dropzone"); let listing = document.getelementbyid("listing"); function scanfiles(item, container) { let elem = document.createelement("li"); elem.innerhtml = item.name; container.appendchild(elem); if (item.isdirectory) { let directoryreader = item.createreader(); let directorycontainer = document.createelement("ul"); container.appendchild(directorycontainer); directoryr...

FormData() - Web APIs
let myform = document.getelementbyid('myform'); let formdata = new formdata(myform); specifications specification status comment xmlhttprequestthe definition of 'formdata()' in that specification.

Guide to the Fullscreen API - Web APIs
let's consider this <video> element: <video controls id="myvideo"> <source src="somevideo.webm"></source> <source src="somevideo.mp4"></source> </video> we can put that video into full-screen mode as follows: var elem = document.getelementbyid("myvideo"); if (elem.requestfullscreen) { elem.requestfullscreen(); } this code checks for the existence of the requestfullscreen() method before calling it.

GeolocationCoordinates.longitude - Web APIs
let button = document.getelementbyid("get-location"); let lattext = document.getelementbyid("latitude"); let longtext = document.getelementbyid("longitude"); button.addeventlistener("click", function() { navigator.geolocation.getcurrentposition(function(position) { let lat = position.coords.latitude; let long = position.coords.longitude; lattext.innertext = lat.tofixed(2); longtext.innertext = long.tofixed(2); ...

GlobalEventHandlers.onchange - Web APIs
html <input type="text" placeholder="type something here, then click outside of the field." size="50"> <p id="log"></p> javascript let input = document.queryselector('input'); let log = document.getelementbyid('log'); input.onchange = handlechange; function handlechange(e) { log.textcontent = `the field's value is ${e.target.value.length} character(s) long.`; } result specification specification status comment html living standardthe definition of 'onchange' in that specification.

GlobalEventHandlers.ondblclick - Web APIs
html <p>double click anywhere in this example.</p> <p id="log"></p> javascript let log = document.getelementbyid('log'); document.ondblclick = logdoubleclick; function logdoubleclick(e) { log.textcontent = `position: (${e.clientx}, ${e.clienty})`; } result specifications specification status comment html living standardthe definition of 'ondblclick' in that specification.

GlobalEventHandlers.ondrag - Web APIs
ck; } </style> </head> <script> function drag_handler(ev) { console.log("drag"); } function dragstart_handler(ev) { console.log("dragstart"); ev.datatransfer.setdata("text", ev.target.id); } function drop_handler(ev) { console.log("drop"); ev.currenttarget.style.background = "lightyellow"; ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragover_handler(ev) { console.log("dragover"); ev.preventdefault(); } </script> <body> <h1>examples of <code>ondrag</code>, <code>ondrop</code>, <code>ondragstart</code>, <code>ondragover</code></h1> <div> <!-- <div class="source"> --> <p id="source" ondrag="drag_handler(event);" ondragstart="dragstart_handler(event);" draggable="true"> select this element, drag it...

GlobalEventHandlers.ondragover - Web APIs
ck; } </style> </head> <script> function drag_handler(ev) { console.log("drag"); } function dragstart_handler(ev) { console.log("dragstart"); ev.datatransfer.setdata("text", ev.target.id); } function drop_handler(ev) { console.log("drop"); ev.currenttarget.style.background = "lightyellow"; ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragover_handler(ev) { console.log("dragover"); ev.preventdefault(); } </script> <body> <h1>examples of <code>ondrag</code>, <code>ondrop</code>, <code>ondragstart</code>, <code>ondragover</code></h1> <div> <p id="source" ondrag="drag_handler(event);" ondragstart="dragstart_handler(event);" draggable="true"> select this element, drag it to the drop zone and then rel...

GlobalEventHandlers.ondragstart - Web APIs
ck; } </style> </head> <script> function drag_handler(ev) { console.log("drag"); } function dragstart_handler(ev) { console.log("dragstart"); ev.datatransfer.setdata("text", ev.target.id); } function drop_handler(ev) { console.log("drop"); ev.currenttarget.style.background = "lightyellow"; ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragover_handler(ev) { console.log("dragover"); ev.preventdefault(); } </script> <body> <h1>examples of <code>ondrag</code>, <code>ondrop</code>, <code>ondragstart</code>, <code>ondragover</code></h1> <div> <p id="source" ondrag="drag_handler(event);" ondragstart="dragstart_handler(event);" draggable="true"> select this element, drag it to the drop zone and then rel...

GlobalEventHandlers.ondrop - Web APIs
ck; } </style> </head> <script> function drag_handler(ev) { console.log("drag"); } function dragstart_handler(ev) { console.log("dragstart"); ev.datatransfer.setdata("text", ev.target.id); } function drop_handler(ev) { console.log("drop"); ev.currenttarget.style.background = "lightyellow"; ev.preventdefault(); var data = ev.datatransfer.getdata("text"); ev.target.appendchild(document.getelementbyid(data)); } function dragover_handler(ev) { console.log("dragover"); ev.preventdefault(); } </script> <body> <h1>examples of <code>ondrag</code>, <code>ondrop</code>, <code>ondragstart</code>, <code>ondragover</code></h1> <div class="source"> <p id="source" ondrag="drag_handler(event);" ondragstart="dragstart_handler(event);" draggable="true"> select this element, drag it to the drop zo...

GlobalEventHandlers.ongotpointercapture - Web APIs
example function overhandler(event) { // determine the target event's gotpointercapture handler let gotcapturehandler = event.target.ongotpointercapture; } function init() { let el = document.getelementbyid('target'); el.ongotpointercapture = overhandler; } specifications specification status comment pointer events – level 2the definition of 'ongotpointercapture' in that specification.

GlobalEventHandlers.oninput - Web APIs
html <input type="text" placeholder="type something here to see its length." size="50"> <p id="log"></p> javascript let input = document.queryselector('input'); let log = document.getelementbyid('log'); input.oninput = handleinput; function handleinput(e) { log.textcontent = `the field's value is ${e.target.value.length} character(s) long.`; } result specifications specification status comment html living standardthe definition of 'oninput' in that specification.

GlobalEventHandlers.oninvalid - Web APIs
thanks!</p> javascript const form = document.getelementbyid('form'); const error = document.getelementbyid('error'); const city = document.getelementbyid('city'); const thanks = document.getelementbyid('thanks'); city.oninvalid = invalid; form.onsubmit = submit; function invalid(event) { error.removeattribute('hidden'); } function submit(event) { form.setattribute('hidden', ''); thanks.removeattribute('hidden'); // for this example, don't actu...

GlobalEventHandlers.onkeydown - Web APIs
html <input> <p id="log"></p> javascript const input = document.queryselector('input'); const log = document.getelementbyid('log'); input.onkeydown = logkey; function logkey(e) { log.textcontent += ` ${e.code}`; } result specifications specification status comment html living standardthe definition of 'onkeydown' in that specification.

GlobalEventHandlers.onkeypress - Web APIs
html <input> <p id="log"></p> javascript const input = document.queryselector('input'); const log = document.getelementbyid('log'); input.onkeypress = logkey; function logkey(e) { log.textcontent += ` ${e.code}`; } result filter keys with a regular expression this example filters the characters typed into a form field using a regular expression.

GlobalEventHandlers.onkeyup - Web APIs
html <input> <p id="log"></p> javascript const input = document.queryselector('input'); const log = document.getelementbyid('log'); input.onkeyup = logkey; function logkey(e) { log.textcontent += ` ${e.code}`; } result specifications specification status comment html living standardthe definition of 'onkeyup' in that specification.

GlobalEventHandlers.onlostpointercapture - Web APIs
example function overhandler(event) { // determine the target event's lostpointercapture handler let lostcapturehandler = event.target.onlostpointercapture; } function init() { let el = document.getelementbyid('target'); el.onlostpointercapture = overhandler; } specifications specification status comment pointer events – level 2the definition of 'onlostpointercapture' in that specification.

GlobalEventHandlers.onpointercancel - Web APIs
<html> <script> function cancelhandler(ev) { // process the pointercancel event } function init() { var el = document.getelementbyid('target1'); el.onpointercancel = cancelhandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onpointerdown - Web APIs
var targetbox = document.getelementbyid("target"); targetbox.onpointerdown = handledown; function handledown(evt) { var action; switch(evt.pointertype) { case "mouse": action = "clicking"; break; case "pen": action = "tapping"; break; case "touch": action = "touching"; break; default: action = "interacting with"; break; } targetbox.innerhtml = "<strong>thanks f...

GlobalEventHandlers.onpointerenter - Web APIs
<html> <script> function enterhandler(ev) { // process the pointerenter event } function init() { let el = document.getelementbyid('target1'); el.onpointerenter = enterhandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onpointerleave - Web APIs
<html> <script> function leavehandler(ev) { // process the pointerleave event } function init() { var el=document.getelementbyid("target1"); el.onpointerleave = leavehandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onpointermove - Web APIs
<html> <script> function movehandler(ev) { // process the pointermove event } function init() { let el=document.getelementbyid('target1'); el.onpointermove = movehandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onpointerout - Web APIs
<html> <script> function outhandler(ev) { // process the pointerout event } function init() { let el=document.getelementbyid('target1'); el.onpointerout = outhandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onpointerover - Web APIs
<html> <script> function overhandler(ev) { // process the pointerover event } function init() { let el = document.getelementbyid('target1'); el.onpointerover = overhandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onpointerup - Web APIs
<html> <script> function uphandler(ev) { // process the pointerup event } function init() { let el = document.getelementbyid('target1'); el.onpointerup = uphandler; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.onreset - Web APIs
time stamp: ${event.timestamp}`; } const form = document.getelementbyid('form'); const log = document.getelementbyid('log'); form.onreset = logreset; result specification specification status comment html living standardthe definition of 'onreset' in that specification.

GlobalEventHandlers.onscroll - Web APIs
html <textarea>1 2 3 4 5 6 7 8 9</textarea> <p id="log"></p> css textarea { width: 4rem; height: 8rem; font-size: 3rem; } javascript const textarea = document.queryselector('textarea'); const log = document.getelementbyid('log'); textarea.onscroll = logscroll; function logscroll(e) { log.textcontent = `scroll position: ${e.target.scrolltop}`; } result specifications specification status comment html living standardthe definition of 'onscroll' in that specification.

GlobalEventHandlers.onselect - Web APIs
html <textarea>try selecting some text in this element.</textarea> <p id="log"></p> javascript function logselection(event) { const log = document.getelementbyid('log'); const selection = event.target.value.substring(event.target.selectionstart, event.target.selectionend); log.textcontent = `you selected: ${selection}`; } const textarea = document.queryselector('textarea'); textarea.onselect = logselection; result specification specification status comment html living standardthe definition of 'onselect' in that specifica...

GlobalEventHandlers.onsubmit - Web APIs
thanks!</p> javascript const form = document.getelementbyid('form'); const error = document.getelementbyid('error'); const city = document.getelementbyid('city'); const thanks = document.getelementbyid('thanks'); city.oninvalid = invalid; form.onsubmit = submit; function invalid(event) { error.removeattribute('hidden'); } function submit(event) { form.setattribute('hidden', ''); thanks.removeattribute('hidden'); // for this example, don't actu...

GlobalEventHandlers.ontouchcancel - Web APIs
<html> <script> function canceltouch(ev) { // process the event } function init() { let el = document.getelementbyid('target1'); el.ontouchcancel = canceltouch; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.ontouchend - Web APIs
<html> <script> function endtouch(ev) { // process the event } function init() { var el=document.getelementbyid("target1"); el.ontouchend = endtouch; } </script> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.ontouchmove - Web APIs
<html> <head> <script> function movetouch(ev) { // process the event } function init() { var el=document.getelementbyid("target1"); el.ontouchmove = movetouch; } </script> </head> <body onload="init();"> <div id="target1"> touch me ...

GlobalEventHandlers.ontouchstart - Web APIs
<html> <script> function starttouch(ev) { // process the event } function init() { let el = document.getelementbyid('target1'); el.ontouchstart = starttouch; } </script> <body onload="init();"> <div id="target1"> touch me ...

HTMLAnchorElement.referrerPolicy - Web APIs
examples var elt = document.createelement("a"); var linktext = document.createtextnode("my link"); elt.appendchild(linktext); elt.href = "https://developer.mozilla.org/"; elt.referrerpolicy = "no-referrer"; var div = document.getelementbyid("divaround"); div.appendchild(elt); // when clicked, the link will not send a referrer header.

HTMLAreaElement.referrerPolicy - Web APIs
examples <img usemap="#maparound" width="100" height="100" src="/img/logo@2x.png" /> <map id="mymap" name="maparound" />> var elt = document.createelement("area"); elt.href = "/img2.png"; elt.shape = "rect"; elt.referrerpolicy = "no-referrer"; elt.coords = "0,0,100,100"; var map = document.getelementbyid("mymap"); map.appendchild(elt); // when clicked, the area's link will not send a referrer header.

HTMLButtonElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <button id="test">button</button> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const button = document.getelementbyid("test"); for(var i = 0; i < button.labels.length; i++) { console.log(button.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLCanvasElement.getContext() - Web APIs
examples given this <canvas> element: <canvas id="canvas" width="300" height="300"></canvas> you can get a 2d context of the canvas with the following code: var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); console.log(ctx); // canvasrenderingcontext2d { ...

HTMLCanvasElement.height - Web APIs
syntax var pxl = canvas.height; canvas.height = pxl; examples given this <canvas> element: <canvas id="canvas" width="300" height="300"></canvas> you can get the height of the canvas with the following code: var canvas = document.getelementbyid('canvas'); console.log(canvas.height); // 300 specifications specification status comment html living standardthe definition of 'htmlcanvaselement.height' in that specification.

HTMLCanvasElement.mozFetchAsStream() - Web APIs
also uses netutil.jsm var canvas = document.getelementbyid('canvas'); var d = canvas.width; ctx = canvas.getcontext('2d'); ctx.beginpath(); ctx.moveto(d / 2, 0); ctx.lineto(d, d); ctx.lineto(0, d); ctx.closepath(); ctx.fillstyle = 'yellow'; ctx.fill(); var netutilcallback = function() { return function(result) { if (!components.issuccesscode(result)) { alert('failed to create icon'); } else { alert('succesfully mad...

HTMLCanvasElement.mozGetAsFile() - Web APIs
function draw() { var canvas = document.getelementbyid('canvas'); var ctx = canvas.getcontext('2d'); ctx.fillstyle = 'rgb(200, 0, 0)'; ctx.fillrect(10, 10, 55, 50); ctx.fillstyle = 'rgba(0, 0, 200, 0.5)'; ctx.fillrect(30, 30, 55, 50); var link = document.getelementbyid('link'); link.addeventlistener('click', copy); } function copy() { var canvas = document.getelementbyid('canvas'); var f = canvas.mozgetasfile('test.png'); var ...

HTMLCanvasElement.mozOpaque - Web APIs
var canvas = document.getelementbyid('canvas'); console.log(canvas.mozopaque); // true // deactivate it canvas.mozopaque = false; specifications not part of any standard.

HTMLCanvasElement.toDataURL() - Web APIs
examples given this <canvas> element: <canvas id="canvas" width="5" height="5"></canvas> you can get a data-url of the canvas with the following lines: var canvas = document.getelementbyid('canvas'); var dataurl = canvas.todataurl(); console.log(dataurl); // "data:image/png;base64,ivborw0kggoaaaansuheugaaaauaaaafcayaaacnby // blaaaadeleqvqimwngobmaaabpaafei8araaaaaelftksuqmcc" setting image quality with jpegs var fullquality = canvas.todataurl('image/jpeg', 1.0); // data:image/jpeg;base64,/9j/4aaqskzjrgabaq...9oadambaairaxeapwd/ad/6ap/z" var mediumquality = canvas.todataurl('ima...

HTMLCanvasElement: webglcontextcreationerror event - Web APIs
bubbles yes cancelable yes interface webglcontextevent event handler property none example var canvas = document.getelementbyid('canvas'); canvas.addeventlistener('webglcontextcreationerror', function(e) { console.log(e.statusmessage || 'unknown error'); }, false); var gl = canvas.getcontext('webgl'); // logs statusmessage or "unknown error" if unable to create webgl context specifications specification status comment webgl 1.0the definition of 'webglcontextcreationerror' in that specificati...

HTMLCanvasElement: webglcontextlost event - Web APIs
bubbles yes cancelable yes interface webglcontextevent event handler property none example with the help of the webgl_lose_context extension, you can simulate the webglcontextlost event: const canvas = document.getelementbyid('canvas'); const gl = canvas.getcontext('webgl'); canvas.addeventlistener('webglcontextlost', (event) => { console.log(event); }); gl.getextension('webgl_lose_context').losecontext(); // "webglcontextlost" event is logged.

HTMLCanvasElement: webglcontextrestored event - Web APIs
bubbles yes cancelable yes interface webglcontextevent event handler property none example with the help of the webgl_lose_context extension, you can simulate the webglcontextrestored event: var canvas = document.getelementbyid('canvas'); var gl = canvas.getcontext('webgl'); canvas.addeventlistener('webglcontextrestored', function(e) { console.log(e); }, false); gl.getextension('webgl_lose_context').restorecontext(); // "webglcontextrestored" event is logged.

HTMLCanvasElement.width - Web APIs
syntax var pxl = canvas.width; canvas.width = pxl; examples given this <canvas> element: <canvas id="canvas" width="300" height="300"></canvas> you can get the width of the canvas with the following code: var canvas = document.getelementbyid('canvas'); console.log(canvas.width); // 300 specifications specification status comment html living standardthe definition of 'htmlcanvaselement.width' in that specification.

HTMLDialogElement.close() - Web APIs
option>red panda</option> <option>spider monkey</option> </select></p> </section> <menu> <button id="cancel" type="reset">cancel</button> <button type="submit">confirm</button> </menu> </form> </dialog> <menu> <button id="updatedetails">update details</button> </menu> <script> (function() { var updatebutton = document.getelementbyid('updatedetails'); var cancelbutton = document.getelementbyid('cancel'); var dialog = document.getelementbyid('favdialog'); dialog.returnvalue = 'favanimal'; function opencheck(dialog) { if(dialog.open) { console.log('dialog open'); } else { console.log('dialog closed'); } } // update button opens a modal dialog ...

HTMLDialogElement.open - Web APIs
option>red panda</option> <option>spider monkey</option> </select></p> </section> <menu> <button id="cancel" type="reset">cancel</button> <button type="submit">confirm</button> </menu> </form> </dialog> <menu> <button id="updatedetails">update details</button> </menu> <script> (function() { var updatebutton = document.getelementbyid('updatedetails'); var cancelbutton = document.getelementbyid('cancel'); var dialog = document.getelementbyid('favdialog'); dialog.returnvalue = 'favanimal'; function opencheck(dialog) { if(dialog.open) { console.log('dialog open'); } else { console.log('dialog closed'); } } // update button opens a modal dialog ...

HTMLDialogElement.returnValue - Web APIs
<option>brine shrimp</option> <option>red panda</option> <option>spider monkey</option> </select> </label></p> <menu> <button>cancel</button> <button>confirm</button> </menu> </form> </dialog> <menu> <button id="updatedetails">update details</button> </menu> <script> (function() { var updatebutton = document.getelementbyid('updatedetails'); var dialog = document.getelementbyid('favdialog'); dialog.returnvalue = 'favanimal'; function opencheck(dialog) { if (dialog.open) { console.log('dialog open'); } else { console.log('dialog closed'); } } function handleuserinput(returnvalue) { if (returnvalue === 'cancel' || returnvalue == null) ...

HTMLDialogElement.show() - Web APIs
option>red panda</option> <option>spider monkey</option> </select></p> </section> <menu> <button id="cancel" type="reset">cancel</button> <button type="submit">confirm</button> </menu> </form> </dialog> <menu> <button id="updatedetails">update details</button> </menu> <script> (function() { var updatebutton = document.getelementbyid('updatedetails'); var cancelbutton = document.getelementbyid('cancel'); var dialog = document.getelementbyid('favdialog'); dialog.returnvalue = 'favanimal'; function opencheck(dialog) { if(dialog.open) { console.log('dialog open'); } else { console.log('dialog closed'); } } // update button opens a modal dialog ...

HTMLDialogElement.showModal() - Web APIs
option>red panda</option> <option>spider monkey</option> </select></p> </section> <menu> <button id="cancel" type="reset">cancel</button> <button type="submit">confirm</button> </menu> </form> </dialog> <menu> <button id="updatedetails">update details</button> </menu> <script> (function() { var updatebutton = document.getelementbyid('updatedetails'); var cancelbutton = document.getelementbyid('cancel'); var dialog = document.getelementbyid('favdialog'); dialog.returnvalue = 'favanimal'; function opencheck(dialog) { if(dialog.open) { console.log('dialog open'); } else { console.log('dialog closed'); } } // update button opens a modal dialog ...

HTMLDialogElement - Web APIs
option>red panda</option> <option>spider monkey</option> </select></p> </section> <menu> <button id="cancel" type="reset">cancel</button> <button type="submit">confirm</button> </menu> </form> </dialog> <menu> <button id="updatedetails">update details</button> </menu> <script> (function() { var updatebutton = document.getelementbyid('updatedetails'); var cancelbutton = document.getelementbyid('cancel'); var dialog = document.getelementbyid('favdialog'); dialog.returnvalue = 'favanimal'; function opencheck(dialog) { if(dialog.open) { console.log('dialog open'); } else { console.log('dialog closed'); } } // update button opens a modal dialog ...

accessKeyLabel - Web APIs
syntax label = element.accesskeylabel example javascript var node = document.getelementbyid('btn1'); if (node.accesskeylabel) { node.title += ' [' + node.accesskeylabel + ']'; } else { node.title += ' [' + node.accesskey + ']'; } node.onclick = function () { var p = document.createelement('p'); p.textcontent = 'clicked!'; node.parentnode.appendchild(p); }; html <button accesskey="h" title="caption" id="btn1">hover me</button> result specifications specification status comment html living standardthe definition of 'htmlelement.accesskeylabel' in that specification.

HTMLElement: beforeinput event - Web APIs
html <input placeholder="enter some text" name="name"/> <p id="values"></p> javascript const input = document.queryselector('input'); const log = document.getelementbyid('values'); input.addeventlistener('beforeinput', updatevalue); function updatevalue(e) { log.textcontent = e.target.value; } result specifications specification status ui eventsthe definition of 'beforeinput event' in that specification.

HTMLElement: change event - Web APIs
html <input placeholder="enter some text" name="name"/> <p id="log"></p> javascript const input = document.queryselector('input'); const log = document.getelementbyid('log'); input.addeventlistener('change', updatevalue); function updatevalue(e) { log.textcontent = e.target.value; } result specifications specification status html living standardthe definition of 'change' in that specification.

HTMLElement.click() - Web APIs
syntax element.click() example simulate a mouse-click when moving the mouse pointer over a checkbox: html <form> <input type="checkbox" id="mycheck" onmouseover="myfunction()" onclick="alert('click event occured')"> </form> javascript // on mouse-over, execute myfunction function myfunction() { document.getelementbyid("mycheck").click(); } specification specification status comment html living standard living standard document object model (dom) level 2 html specification obsolete initial definition.

HTMLElement.contextMenu - Web APIs
syntax var elementcontextmenu = element.contextmenu; example var contextmenu = document.getelementbyid("element").contextmenu; // change the label of the first menu entry contextmenu.firstelementchild.label = "new label"; ...

HTMLElement.dir - Web APIs
example var parg = document.getelementbyid("para1"); parg.dir = "rtl"; // change the text direction on a paragraph identified as "para1" specifications specification status comment html living standardthe definition of 'dir' in that specification.

HTMLElement.hidden - Web APIs
javascript document.getelementbyid("okbutton") .addeventlistener("click", function() { document.getelementbyid("welcome").hidden = true; document.getelementbyid("awesome").hidden = false; }, false); this code sets up a handler for the welcome panel's "ok" button that hides the welcome panel and makes the follow-up panel—with the curious name "awesome"—visible in its place.

HTMLElement.innerText - Web APIs
e; }</style> <span id=text>take a look at<br>how this text<br>is interpreted below.</span> <span style="display:none">hidden text</span> </p> <h3>result of textcontent:</h3> <textarea id="textcontentoutput" rows="6" cols="30" readonly>...</textarea> <h3>result of innertext:</h3> <textarea id="innertextoutput" rows="6" cols="30" readonly>...</textarea> javascript const source = document.getelementbyid("source"); const textcontentoutput = document.getelementbyid("textcontentoutput"); const innertextoutput = document.getelementbyid("innertextoutput"); textcontentoutput.value = source.textcontent; innertextoutput.value = source.innertext; result specification specification status comment html living standardthe definition of 'innertext' in that specification.

HTMLElement: input event - Web APIs
html <input placeholder="enter some text" name="name"/> <p id="values"></p> javascript const input = document.queryselector('input'); const log = document.getelementbyid('values'); input.addeventlistener('input', updatevalue); function updatevalue(e) { log.textcontent = e.target.value; } result specifications specification status html living standardthe definition of 'input event' in that specification.

HTMLElement.isContentEditable - Web APIs
</p> javascript document.getelementbyid('infotext1').innerhtml += document.getelementbyid('mytext1').iscontenteditable; document.getelementbyid('infotext2').innerhtml += document.getelementbyid('mytext2').iscontenteditable; result specifications specification status comment html living standardthe definition of 'htmlelement.contenteditable' in that specification.

HTMLElement.offsetTop - Web APIs
example var d = document.getelementbyid("div1"); var toppos = d.offsettop; if (toppos > 10) { // object is offset more // than 10 pixels from its parent } specification specification status comment css object model (cssom) view modulethe definition of 'offsettop' in that specification.

HTMLElement.oncopy - Web APIs
html <h3>play with this text area:</h3> <textarea id="editor" rows="3">try copying and pasting text into this field!</textarea> <h3>log:</h3> <p id="log"></p> javascript const log = document.getelementbyid('log'); function logcopy(event) { log.innertext = 'copy blocked!\n' + log.innertext; event.preventdefault(); } function logpaste(event) { log.innertext = 'paste blocked!\n' + log.innertext; event.preventdefault(); } const editor = document.getelementbyid('editor'); editor.oncopy = logcopy; editor.onpaste = logpaste; result specification whatwg standard ...

HTMLElement.oncut - Web APIs
html <h3>play with this text area:</h3> <textarea id="editor" rows="3">try copying and cutting the text in this field!</textarea> <h3>log:</h3> <p id="log"></p> javascript function logcopy(event) { log.innertext = 'copied!\n' + log.innertext; } function preventcut(event) { event.preventdefault(); log.innertext = 'cut blocked!\n' + log.innertext; } const editor = document.getelementbyid('editor'); const log = document.getelementbyid('log'); editor.oncopy = logcopy; editor.oncut = preventcut; result specification whatwg standard ...

HTMLElement.onpaste - Web APIs
html <h3>play with this text area:</h3> <textarea id="editor" rows="3">try copying and pasting text into this field!</textarea> <h3>log:</h3> <p id="log"></p> javascript function logcopy(event) { log.innertext = 'copied!\n' + log.innertext; } function logpaste(event) { log.innertext = 'pasted!\n' + log.innertext; } const editor = document.getelementbyid('editor'); const log = document.getelementbyid('log'); editor.oncopy = logcopy; editor.onpaste = logpaste; result specification whatwg standard ...

HTMLFontElement.color - Web APIs
name color string nameofcolor (case insensitive) green green green valid hex color string in rgb format: #rrggbb #008000 rgb using decimal values rgb(x,x,x) (x in 0-255 range) rgb(0,128,0) syntax colorstring = fontobj.color; fontobj.color = colorstring; examples // assumes there is <font id="f"> element in the html var f = document.getelementbyid("f"); f.color = "green"; specifications the <font> tag is not supported in html5 and as a result neither is <font>.color.

HTMLFontElement.face - Web APIs
g must follow one of the following html microsyntax: microsyntax description examples list of one or more valid font family names a list of font names, that have to be present on the local system courier,verdana syntax facestring = fontobj.face; fontobj.face = facestring; examples // assumes there is <font id="f"> element in the html var f = document.getelementbyid("f"); f.face = "arial"; specifications the <font> tag is not supported in html5 and as a result neither is <font>.face .

HTMLFontElement.size - Web APIs
ng integer number in the range of 1-7 6 relative size string +x or -x, where x is the number relative to the value of the size attribute of the <basefont> element (the result should be in the same range of 1-7) +2 -1 syntax sizestring = fontobj.size; fontobj.size = sizestring; examples // assumes there is <font id="f"> element in the html var f = document.getelementbyid("f"); f.size = "6"; specifications the <font> tag is not supported in html5 and as a result neither is <font>.size .

HTMLFormElement.length - Web APIs
example if (document.getelementbyid('form1').length > 1) { // more than one form control here } specifications specification status comment html living standardthe definition of 'htmlformelement: length' in that specification.

HTMLFormElement.name - Web APIs
syntax var string = form.name; form.name = string; example var form1name = document.getelementbyid('form1').name; if (form1name != document.form.form1) { // browser doesn't support this form of reference } specifications specification status comment html living standardthe definition of 'htmlformelement: name' in that specification.

HTMLFormElement.reset() - Web APIs
syntax htmlformelement.reset() example document.getelementbyid('myform').reset(); specifications specification status comment html living standardthe definition of 'htmlformelement: reset' in that specification.

HTMLFormElement: reset event - Web APIs
time stamp: ${event.timestamp}`; } const form = document.getelementbyid('form'); const log = document.getelementbyid('log'); form.addeventlistener('reset', logreset); result specifications specification status comment html living standardthe definition of 'reset' in that specification.

HTMLFormElement: submit event - Web APIs
time stamp: ${event.timestamp}`; event.preventdefault(); } const form = document.getelementbyid('form'); const log = document.getelementbyid('log'); form.addeventlistener('submit', logsubmit); result specifications specification status comment html living standardthe definition of 'submit' in that specification.

HTMLHyperlinkElementUtils.hash - Web APIs
syntax string = object.hash; object.hash = string; examples <a id="myanchor" href="/docs/htmlhyperlinkelementutils.href#examples">examples</a> <script> var anchor = document.getelementbyid("myanchor"); console.log(anchor.hash); // returns '#examples' </script> specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.hash' in that specification.

HTMLHyperlinkElementUtils.hostname - Web APIs
syntax string = object.hostname; object.hostname = string; examples // let's an <a id="myanchor" href="https://developer.mozilla.org/docs/htmlhyperlinkelementutils.hostname"> element be in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.hostname; // returns:'developer.mozilla.org' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.hostname' in that specification.

HTMLHyperlinkElementUtils.href - Web APIs
syntax string = object.href; object.href = string; examples // lets imagine an <a id="myanchor" href="https://developer.mozilla.org/htmlhyperlinkelementutils/href"> element is in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.href; // returns: 'https://developer.mozilla.org/htmlhyperlinkelementutils/href' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.href' in that specification.

HTMLHyperlinkElementUtils.password - Web APIs
syntax string = object.password; object.password = string; examples // let's <a id="myanchor" href="https://anonymous:flabada@developer.mozilla.org/docs/htmlhyperlinkelementutils.username"> be in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.password; // returns:'flabada' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.password' in that specification.

HTMLHyperlinkElementUtils.pathname - Web APIs
syntax string = object.pathname; object.pathname = string; examples // let's an <a id="myanchor" href="https://developer.mozilla.org/docs/htmlhyperlinkelementutils.pathname"> element be in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.pathname; // returns:'/docs/htmlhyperlinkelementutils.pathname' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.pathname' in that specification.

HTMLHyperlinkElementUtils.port - Web APIs
syntax string = object.port; object.port = string; examples // let's an <a id="myanchor" href="https://developer.mozilla.org:443/docs/htmlhyperlinkelementutils.port"> element be in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.port; // returns:'443' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.port' in that specification.

HTMLHyperlinkElementUtils.protocol - Web APIs
syntax string = object.protocol; object.protocol = string; examples // let's an <a id="myanchor" href="https://developer.mozilla.org/htmlhyperlinkelementutils.protocol"> element be in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.protocol; // returns:'https:' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.protocol' in that specification.

HTMLHyperlinkElementUtils.search - Web APIs
syntax string = object.search; object.search = string; examples // let an <a id="myanchor" href="https://developer.mozilla.org/docs/htmlhyperlinkelementutils.search?q=123"> element be in the document var anchor = document.getelementbyid("myanchor"); var querystring = anchor.search; // returns:'?q=123' // further parsing: let params = new urlsearchparams(querystring); let q = parseint(params.get("q")); // is the number 123 specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.search' in that specification.

HTMLHyperlinkElementUtils.toString() - Web APIs
syntax string = object.tostring(); examples // let's imagine an <a id="myanchor" href="https://developer.mozilla.org/docs/htmlhyperlinkelementutils/tostring"> element is in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.tostring(); // returns: 'https://developer.mozilla.org/docs/htmlhyperlinkelementutils/tostring' specifications specification status comment html living standard living standard ...

HTMLHyperlinkElementUtils.username - Web APIs
syntax string = object.username; object.username = string; examples // let's <a id="myanchor" href="https://anonymous:flabada@developer.mozilla.org/docs/htmlhyperlinkelementutils.username"> be in the document var anchor = document.getelementbyid("myanchor"); var result = anchor.username; // returns:'anonymous' specifications specification status comment html living standardthe definition of 'htmlhyperlinkelementutils.username' in that specification.

HTMLImageElement.referrerPolicy - Web APIs
examples var img = new image(); img.src = 'img/logo.png'; img.referrerpolicy = 'origin'; var div = document.getelementbyid('divaround'); div.appendchild(img); // fetch the image using the origin as the referrer specifications specification status comment referrer policythe definition of 'referrerpolicy attribute' in that specification.

HTMLImageElement.sizes - Web APIs
let image = document.queryselector("article img"); let break40 = document.getelementbyid("break40"); let break50 = document.getelementbyid("break50"); break40.addeventlistener("click", event => image.sizes = image.sizes.replace(/50em,/, "40em,")); break50.addeventlistener("click", event => image.sizes = image.sizes.replace(/40em,/, "50em,")); result this result may be viewed in its own window here.

HTMLImageElement.x - Web APIs
let logbox = document.queryselector("pre"); let tbl = document.getelementbyid("userinfo") let log = msg => { logbox.innerhtml += `${msg}<br>`; } let cell = tbl.rows[1].cells[2]; let image = cell.queryselector("img"); log(`image's global x: ${image.x}`); log(`image's global y: ${image.y}`); this uses the <table>'s rows property to get a list of the rows in the table, from which it looks up row 1 (which, being a zero-based index, means the second row from the top).

HTMLImageElement.y - Web APIs
let logbox = document.queryselector("pre"); let tbl = document.getelementbyid("userinfo") let log = msg => { logbox.innerhtml += `${msg}<br>`; } let cell = tbl.rows[1].cells[2]; let image = cell.queryselector("img"); log(`image's global x: ${image.x}`); log(`image's global y: ${image.y}`); this uses the <table>'s rows property to get a list of the rows in the table, from which it looks up row 1 (which, being a zero-based index, means the second row from the top).

HTMLInputElement: invalid event - Web APIs
html <form action="#"> <ul> <li><label>enter an integer between 1 and 10: <input type="number" min="1" max="10" required></label></li> <li><input type="submit" value="submit"></li> </ul> </form><p id="log"></p> javascript const input = document.queryselector('input') const log = document.getelementbyid('log') input.addeventlistener('invalid', logvalue) function logvalue(e) { log.textcontent += e.target.value } result specifications specification status comment html living standardthe definition of 'invalid event' in that specification.

HTMLInputElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <input id="test"/> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const input = document.getelementbyid("test"); for(var i = 0; i < input.labels.length; i++) { console.log(input.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLInputElement.multiple - Web APIs
example // fileinput is a <input type=file multiple> let fileinput = document.getelementbyid('myfileinput'); if (fileinput.multiple == true) { for (let i = 0; i < fileinput.files.length; i++) { // loop fileinput.files } // only one file available } else { let file = fileinput.files.item(0); } ...

HTMLInputElement.select() - Web APIs
html <input type="text" id="text-box" size="20" value="hello world!"> <button onclick="selecttext()">select text</button> javascript function selecttext() { const input = document.getelementbyid('text-box'); input.focus(); input.select(); } result notes calling element.select() will not necessarily focus the input, so it is often used with htmlelement.focus().

HTMLInputElement.setRangeText() - Web APIs
html <input type="text" id="text-box" size="30" value="this text has not been updated."> <button onclick="selecttext()">update text</button> javascript function selecttext() { const input = document.getelementbyid('text-box'); input.focus(); input.setrangetext('already', 14, 17, 'select'); } result specifications specification status comment html living standardthe definition of 'htmlinputelement.setselectionrange()' in that specification.

HTMLInputElement.setSelectionRange() - Web APIs
html <input type="text" id="text-box" size="20" value="mozilla"> <button onclick="selecttext()">select text</button> javascript function selecttext() { const input = document.getelementbyid('text-box'); input.focus(); input.setselectionrange(2, 5); } result specifications specification status comment html living standardthe definition of 'htmlinputelement.setselectionrange()' in that specification.

HTMLInputElement.stepDown() - Web APIs
e by 5: <input type="number" step="5" id="thenumber" min="0" max="400"> </label> </p> <p> <label>enter how many values of step you would like to increment by or leave it blank: <input type="number" step="1" id="decrementer" min="-2" max="15"> </label> </p> <input type="button" value="decrement" id="thebutton"> javascript /* make the button call the function */ let button = document.getelementbyid('thebutton'); button.addeventlistener('click', function() { stepondown();} ); function stepondown() { let input = document.getelementbyid('thenumber'); let val = document.getelementbyid('decrementer').value; if (val) { /* increment with a parameter */ input.stepdown(val); } else { /* or without a parameter.

HTMLInputElement.stepUp() - Web APIs
le by 5: <input type="number" step="5" id="thenumber" min="0" max="400"> </label> </p> <p> <label>enter how many values of step you would like to increment by or leave it blank: <input type="number" step="1" id="incrementer" min="0" max="25"> </label> </p> <input type="button" value="increment" id="thebutton"> javascript /* make the button call the function */ let button = document.getelementbyid('thebutton') button.addeventlistener('click', function() { steponup() }) function steponup() { let input = document.getelementbyid('thenumber') let val = document.getelementbyid('incrementer').value if (val) { /* increment with a parameter */ input.stepup(val) } else { /* or without a parameter.

HTMLInputElement.webkitEntries - Web APIs
html <input id="files" type="file" multiple> javascript document.getelementbyid("files").addeventlistener("change", function(event) { event.target.webkitentries.foreach(function(entry) { /* do stuff with the entry */ }); }); each time a change event occurs, this code iterates over the selected files, obtaining their filesystementry-based objects and acting on them.

HTMLInputElement.webkitdirectory - Web APIs
html content <input type="file" id="filepicker" name="filelist" webkitdirectory multiple /> <ul id="listing"></ul> javascript content document.getelementbyid("filepicker").addeventlistener("change", function(event) { let output = document.getelementbyid("listing"); let files = event.target.files; for (let i=0; i<files.length; i++) { let item = document.createelement("li"); item.innerhtml = files[i].webkitrelativepath; output.appendchild(item); }; }, false); result specifications specification status comment ...

HTMLMediaElement.audioTracks - Web APIs
var video = document.getelementbyid("video"); for (var i = 0; i < video.audiotracks.length; i += 1) { video.audiotracks[i].enabled = false; } specifications specification status comment html living standardthe definition of 'htmlmediaelement.audiotracks' in that specification.

HTMLMediaElement.captureStream() - Web APIs
document.queryselector('.playandrecord').addeventlistener('click', function() { var playbackelement = document.getelementbyid("playback"); var capturestream = playbackelement.capturestream(); playbackelement.play(); }); see recording a media element for a longer and more intricate example and explanation.

HTMLMediaElement.fastSeek() - Web APIs
let myvideo = document.getelementbyid("myvideoelement"); myvideo.fastseek(20); specifications specification status comment html living standardthe definition of 'fastseek()' in that specification.

HTMLMediaElement.networkState - Web APIs
<audio id="example" preload="auto"> <source src="sound.ogg" type="audio/ogg" /> </audio> var obj = document.getelementbyid('example'); obj.addeventlistener('playing', function() { if (obj.networkstate === 2) { // still loading...

HTMLMediaElement.play() - Web APIs
example this example demonstrates how to confirm that playback has begun and how to gracefully handle blocked automatic playback: let videoelem = document.getelementbyid("video"); let playbutton = document.getelementbyid("playbutton"); playbutton.addeventlistener("click", handleplaybutton, false); playvideo(); async function playvideo() { try { await videoelem.play(); playbutton.classlist.add("playing"); } catch(err) { playbutton.classlist.remove("playing"); } } function handleplaybutton() { if (videoelem.paused) { playvideo(); } else...

HTMLMediaElement.readyState - Web APIs
<audio id="example" preload="auto"> <source src="sound.ogg" type="audio/ogg" /> </audio> var obj = document.getelementbyid('example'); obj.addeventlistener('loadeddata', function() { if(obj.readystate >= 2) { obj.play(); } }); specifications specification status comment html living standardthe definition of 'htmlmediaelement.readystate' in that specification.

HTMLMeterElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <meter id="test" min="0" max="100" value="70">70</meter> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const meter = document.getelementbyid("test"); for(var i = 0; i < meter.labels.length; i++) { console.log(meter.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLObjectElement.setCustomValidity - Web APIs
function validate(inputid) { var input = document.getelementbyid(inputid); var validitystate_object = input.validity; if (validitystate_object.valuemissing) { input.setcustomvalidity('you gotta fill this out, yo!'); input.reportvalidity(); } else if (input.rangeunderflow) { input.setcustomvalidity('we need a higher number!'); input.reportvalidity(); } else if (input.rangeoverflow) { input.setcustomvalidity('thats too high!'); input.report...

HTMLObjectElement.typeMustMatch - Web APIs
syntax var mustmatch = obj.typemustmatch; obj.typemustmatch = mustmatch; example html <object id="obj" data="move.swf" type="application/x-shockwave-flash" typemustmatch></object> javascript let obj = document.getelementbyid('obj'); console.log(obj.typemustmatch); specifications specification status comment html5the definition of 'htmlobjectelement' in that specification.

Option() - Web APIs
examples just add new options /* assuming we have the following html <select id='s'> </select> */ var s = document.getelementbyid('s'); var options = [four, five, six]; options.foreach(function(element,key) { s[key] = new option(element,key); }); append options with different parameters /* assuming we have the following html <select id="s"> <option>first</option> <option>second</option> <option>third</option> </select> */ var s = document.getelementbyid('s'); var options = [ 'zero', 'one', 'two' ]; opt...

HTMLElement.blur() - Web APIs
syntax element.blur(); examples remove focus from a text input html <input type="text" id="mytext" value="sample text"> <br><br> <button type="button" onclick="focusinput()">click me to gain focus</button> <button type="button" onclick="blurinput()">click me to lose focus</button> javascript function focusinput() { document.getelementbyid('mytext').focus(); } function blurinput() { document.getelementbyid('mytext').blur(); } result specification specification status comment html living standardthe definition of 'blur' in that specification.

HTMLOrForeignElement.tabIndex - Web APIs
syntax element.tabindex = index; var index = element.tabindex; value index is an integer example const b1 = document.getelementbyid('button1'); b1.tabindex = 1; specifications specification status comment html living standardthe definition of 'tabindex' in that specification.

HTMLOutputElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <output id="test">output</output> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const output = document.getelementbyid("test"); for(var i = 0; i < output.labels.length; i++) { console.log(output.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLProgressElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <progress id="test" value="70" max="100">70%</progress> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const progress = document.getelementbyid("test"); for(var i = 0; i < progress.labels.length; i++) { console.log(progress.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLSelectElement.autofocus - Web APIs
syntaxedit abool = aselectelement.autofocus; // get the value of autofocus aselectelement.autofocus = abool; // set the value of autofocus example html <select id="myselect" autofocus> <option>option 1</option> <option>option 2</option> </select> javascript // check if the autofocus attribute on the <select> var hasautofocus = document.getelementbyid('myselect').autofocus; specifications specification status comment html living standardthe definition of 'autofocus' in that specification.

HTMLSelectElement.disabled - Web APIs
<input id="allow-drinks" type="checkbox"/> </label> <label for="drink-select">drink selection:</label> <select id="drink-select" disabled> <option value="1">water</option> <option value="2">beer</option> <option value="3">pepsi</option> <option value="4">whisky</option> </select> javascript var allowdrinkscheckbox = document.getelementbyid("allow-drinks"); var drinkselect = document.getelementbyid("drink-select"); allowdrinkscheckbox.addeventlistener("change", function(event) { if (event.target.checked) { drinkselect.disabled = false; } else { drinkselect.disabled = true; } }, false); result specifications specification status comment html living standardthe definition of 'disabled' in th...

HTMLSelectElement.form - Web APIs
the below code gives all select elements in a particular form a css class of "selectclass": <script type="text/javascript"> var form_element = document.getelementbyid('subscribe_form'); var vist = form_element.style; if (vist.display=='' || vist.display=='none') { vist.display = 'block'; } else { vist.display = 'none'; } </script> specifications specification status comment html living standardthe definition of 'form' in that specification.

HTMLSelectElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <select id="test"> <option value="1">option 1</option> <option value="2">option 2</option> </select> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const select = document.getelementbyid("test"); for(var i = 0; i < select.labels.length; i++) { console.log(select.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLSelectElement.options - Web APIs
example html <label for="test">label</label> <select id="test"> <option value="1">option 1</option> <option value="2">option 2</option> </select> javascript window.addeventlistener("domcontentloaded", function() { const select = document.getelementbyid("test"); for(var i = 0; i < select.options.length; i++) { console.log(select.options[i].label); // "option 1" and "option 2" } }); specifications specification status comment html living standardthe definition of 'options' in that specification.

HTMLSelectElement.remove() - Web APIs
example var sel = document.getelementbyid("existinglist"); sel.remove(1); /* takes the existing following select object: <select id="existinglist" name="existinglist"> <option value="1">option: value 1</option> <option value="2">option: value 2</option> <option value="3">option: value 3</option> </select> and changes it to: <select id="existinglist" name="existinglist"> <option value="1">option: value 1</option> <option value="3">option: value 3<...

HTMLSelectElement.selectedIndex - Web APIs
syntax var index = selectelem.selectedindex; selectelem.selectedindex = index; example html <p id="p">selectedindex: 0</p> <select id="select"> <option selected>option a</option> <option>option b</option> <option>option c</option> <option>option d</option> <option>option e</option> </select> javascript var selectelem = document.getelementbyid('select') var pelem = document.getelementbyid('p') // when a new <option> is selected selectelem.addeventlistener('change', function() { var index = selectelem.selectedindex; // add that data to the <p> pelem.innerhtml = 'selectedindex: ' + index; }) specifications specification status comment html living standardthe definition of 'htmlselectelement' in that spe...

HTMLSelectElement.selectedOptions - Web APIs
javascript the javascript code that establishes the event handler for the button, as well as the event handler itself, looks like this: let orderbutton = document.getelementbyid("order"); let itemlist = document.getelementbyid("foods"); let outputbox = document.getelementbyid("output"); orderbutton.addeventlistener("click", function() { let collection = itemlist.selectedoptions; let output = ""; for (let i=0; i<collection.length; i++) { if (output === "") { output = "your order for the following items has been placed: "; } output += collection[i...

HTMLSelectElement - Web APIs
example get information about the selected option /* assuming we have the following html <select id='s'> <option>first</option> <option selected>second</option> <option>third</option> </select> */ var select = document.getelementbyid('s'); // return the index of the selected option console.log(select.selectedindex); // 1 // return the value of the selected option console.log(select.options[select.selectedindex].value) // second a better way to track changes to the user's selection is to watch for the change event to occur on the <select>.

HTMLStyleElement.media - Web APIs
example <!doctype html> <html> <head> <link id="linkedstyle" rel="stylesheet" href="document.css" type="text/css" media="screen" /> <style id="inlinestyle" rel="stylesheet" type="text/css" media="screen, print"> p { color: blue; } </style> </head> <body> <script> alert('linkedstyle: ' + document.getelementbyid('linkedstyle').media); // 'screen' alert('inlinestyle: ' + document.getelementbyid('inlinestyle').media); // 'screen, print' </script> </body> </html> specifications specification status comment html living standardthe definition of 'htmlstyleelement' in that specification.

HTMLTableElement.align - Web APIs
syntax htmltableelement.align = alignment; var alignment = htmltableelement.align; parameters alignment domstring with one of the following values: left center right example // set the alignmnet of a table var t = document.getelementbyid('tablea'); t.align = 'center'; specification w3c dom 2 html specification htmltableelement .align.

HTMLTableElement.bgColor - Web APIs
example // set table background colour to lightblue var t = document.getelementbyid('tablea'); t.bgcolor = 'lightblue'; specification dom level 2 html:htmltableelement .bgcolor ...

HTMLTableElement.border - Web APIs
example // set the width of a table border to 2 pixels var t = document.getelementbyid('tablea'); t.border = '2'; specification w3c dom 2 html specification htmltableelement .border.

HTMLTableElement.cellPadding - Web APIs
example // set cell padding to 10 pixels let t = document.getelementbyid('tablea'); t.cellpadding = '10'; specification w3c dom 2 html specification htmltableelement .cellpadding.

HTMLTableElement.cellSpacing - Web APIs
var t = document.getelementbyid('tablea'); t.cellspacing = "10"; specification w3c dom 2 html specification htmltableelement .cellspacing.

HTMLTableElement.frame - Web APIs
"above" top side "below" bottom side "hsides" top and bottom only "vsides" right and left sides only "lhs" left-hand side only "rhs" right-hand side only "box" all four sides "border" all four sides example // set the frame of tablea to 'border' var t = document.getelementbyid('tablea'); t.frame = "border"; t.border = "2px"; specification w3c dom 2 html specification ...

HTMLTableElement.rules - Web APIs
syntax htmltableelement.rules = rules; var rules = htmltableelement.rules; parameters rules is a string with one of the following values: none no rules groups lines between groups only rows lines between rows cols lines between cols all lines between all cells example // turn on all the internal borders of a table var t = document.getelementbyid("tableid"); t.rules = "all"; specification w3c dom 2 html specification ...

HTMLTableRowElement.insertCell() - Web APIs
html <table id="my-table"> <tr><td>row 1</td></tr> <tr><td>row 2</td></tr> <tr><td>row 3</td></tr> </table> javascript function addrow(tableid) { // get a reference to the table let tableref = document.getelementbyid(tableid); // insert a row at the end of the table let newrow = tableref.insertrow(-1); // insert a cell in the row at index 0 let newcell = newrow.insertcell(0); // append a text node to the cell let newtext = document.createtextnode('new bottom row'); newcell.appendchild(newtext); } // call addrow() with the table's id addrow('my-table'); result specifications spe...

HTMLTextAreaElement.labels - Web APIs
example html <label id="label1" for="test">label 1</label> <textarea id="test">some text</textarea> <label id="label2" for="test">label 2</label> javascript window.addeventlistener("domcontentloaded", function() { const textarea = document.getelementbyid("test"); for(var i = 0; i < textarea.labels.length; i++) { console.log(textarea.labels[i].textcontent); // "label 1" and "label 2" } }); specifications specification status comment html living standardthe definition of 'labels' in that specification.

HTMLTimeElement.dateTime - Web APIs
pthhmms.xs pthhmms.xxs pthhmms.xxxs ww dd hh mm ss p12dt7h12m13s p12dt7h12m13.3s p12dt7h12m13.45s p12dt7h12m13.455s pt7h12m13s pt7h12m13.2s pt7h12m13.56s pt7h12m13.999s 7d 5h 24m 13s syntax datetimestring = timeelt.datetime; timeelt.datetime = datetimestring example // assumes there is <time id="t"> element in the html var t = document.getelementbyid("t"); t.datetime = "6w 5h 34m 5s"; specifications specification status comment html living standardthe definition of 'htmltimeelement' in that specification.

HTMLTrackElement: cuechange event - Web APIs
let texttrackelem = document.getelementbyid("texttrack"); texttrackelem.addeventlistener("cuechange", (event) => { let cues = event.target.track.activecues; }); in addition, you can use the oncuechange event handler: let texttrackelem = document.getelementbyid("texttrack"); texttrackelem.oncuechange = (event) => { let cues = event.target.track.activecues; }); specifications specification status html living s...

HTMLVideoElement.getVideoPlaybackQuality() - Web APIs
this value includes any dropped or corrupted frames, so it's not the same as "total number of frames played." var videoelem = document.getelementbyid("my_vid"); var counterelem = document.getelementbyid("counter"); var quality = videoelem.getvideoplaybackquality(); counterelem.innertext = quality.totalvideoframes; specifications specification status comment media playback qualitythe definition of 'htmlvideoelement.getvideoplaybackquality()' in that specification.

HTMLVideoElement.msHorizontalMirror - Web APIs
example var myvideo = document.getelementbyid("videotag1"); myvideo.mshorizontalmirror = true; myvideo.play(); example #2: var flip = document.queryselector('#flip'); flip.addeventlistener('click', function() { video.mshorizontalmirror = true; }); see also htmlvideoelement microsoft api extensions ...

HTMLVideoElement.msInsertVideoEffect() - Web APIs
example var ovideo1 = document.getelementbyid("video1"); ovideo1.msinsertvideoeffect("windows.media.videoeffects.videostabilization", true, null); see also htmlvideoelement microsoft api extensions ...

HTMLVideoElement.msZoom - Web APIs
var myvideo = document.getelementbyid("videotag1"); myvideo.mszoom = true; myvideo.play(); see also htmlvideoelement microsoft api extensions ...

HTMLVideoElement.videoHeight - Web APIs
let v = document.getelementbyid("myvideo"); v.addeventlistener("resize", ev => { let w = v.videowidth; let h = v.videoheight; if (w && h) { v.style.width = w; v.style.height = h; } }, false); note that this only applies the change if both the videowidth and the videoheight are non-zero.