Open the debugger - Firefox Developer Tools
there are three ways to open the debugger: select "debugger" from the web developer submenu in the firefox menu (or tools menu if you display the menu bar or are on mac os x) press ctrl + shift + z on windows and linux, or cmd + opt + z on macos (starting in firefox 71; prior to firefox 66, the letter in this shortcut was s).
... press the menu button ( ), select "developer", then "debugger".

Using the Debugger map scopes feature - Firefox Developer Tools
open the example page and then open the debugger using tools > web developer > debugger (or press ctrl + i and then select the debugger).
... the debugger opens the file "increment.js" so you can view the original code.

Debugger keyboard shortcuts - Firefox Developer Tools
note: before firefox 66, the combination ctrl + shift + s on windows and linux or cmd + opt + s on macos would open/close the debugger.

Index - Firefox Developer Tools
17 debugger-api debugger, intermediate, intro, javascript, tools mozilla’s javascript engine, spidermonkey, provides a debugging interface named debugger which lets javascript code observe and manipulate the execution of other javascript code.
... both firefox’s built-in developer tools and the firebug add-on use debugger to implement their javascript debuggers.
... however, debugger is quite general, and can be used to implement other kinds of tools like tracers, coverage analysis, patch-and-continue, and so on.
...And 40 more matches

Venkman Introduction - Archive of obsolete content
the javascript debugger, also called venkman, has been a part of the mozilla browser and the community of web and script developers there for some time.
... this article provides an overview and some practical examples of using the javascript debugger in web applications and web page scripting.
...even if you are already using venkman, the features, procedures, and tips described here will make you a more confident web developer and debugger.
...And 31 more matches

Web Replay
devtools' debugger and console can be used to inspect and control the replay.
... an easy way to see this is to open the debugger developer tool, press the pause button and then the rewind button.
... step back when paused, the reverse step button in the debugger developer tool will step to the previous line executed and allow inspecting program state there.
...And 28 more matches

Tutorial: Set a breakpoint - Firefox Developer Tools
this page shows how you can try out the debugger api yourself using firefox’s scratchpad.
... we use debugger to set a breakpoint in a function, and then evaluate an expression whenever it is hit.
... since the debugger api is only available to privileged javascript code, you’ll need to use the browser content toolbox to try it out.
...And 17 more matches

Debugging on Windows
if vc++ and your mozilla application hang shortly after you launch the application under the debugger, see problems loading debug symbols.
... ways to start the debugger first of all, it's necessary to install a visual studio extension to be able to follow child processes as they are created.
...you can click "start" button to run firefox then, already attached in the debugger.
...And 14 more matches

Index - Archive of obsolete content
192 javascript debugger service code snippets no summary!
...the crash victim should at least know how to run a debugger, if not how to use it, and should have a debug build of firefox handy.
...here's an example: 684 venkman extensions, extensions:tools, javascript, javascript:tools, tools, venkman, web development, web development:tools venkman is the code name for mozilla's javascript debugger.
...And 11 more matches

UI Tour - Firefox Developer Tools
this article is a quick tour of the main sections of the javascript debugger's user interface.
... the ui is split vertically into three panels source list pane source pane the contents of the third pane depend on the current state of the debugger and may include the following sections: toolbar watch expressions breakpoints call stack scopes xhr breakpoints event listener breakpoints dom mutation breakpoints source list pane the source list pane lists all the javascript source files loaded into the page, and enables you to select one to debug.
... ignore source causes the debugger to skip the file when "stepping into" functions; this can be helpful for avoiding stepping into libraries used by your code.
...And 10 more matches

Web Console remoting - Firefox Developer Tools
to better understand the architecture of the web console we recommend learning about the debugger architecture.
... to see how the debugger is used in the web console code, look in browser/devtools/webconsole/webconsole.js, and search for webconsoleconnectionproxy.
... to attach to the webconsoleactor, follow these steps: connecttoserver() // the usual listtabs() pickthetabyouwant() debuggerclient.attachconsole(tab.consoleactor, listeners, onattachconsole) the listeners argument is an array which specifies listeners you want to start in the web console.
...And 9 more matches

Venkman - Archive of obsolete content
venkman is the code name for mozilla's javascript debugger.
... documentation venkman introduction an overview and some practical examples of using the javascript debugger in web development.
... learning the javascript debugger venkman written by svend tofte to the javascript programmers who are not familiar with other debugging tools.
...And 7 more matches

WebReplayRoadmap
without time travel, using the console requires repeatedly updating the source or the debugger's log points, reloading, and reproducing the bug.
... this is based on the logpoints feature in the debugger, which can be enabled with the devtools.debugger.features.log-points preference.
... new features are possible with time travel, though, which would be nice to support: supporting the debugger's event breakpoints would allow searching the recording for places where particular dom events occur, and -- in the same manner as logpoints -- logging them to the console and allowing them to be seeked to later.
...And 7 more matches

dev/panel - Archive of obsolete content
individual built-in tools, such as the javascript debugger or the web console, occupy "panels" in the toolbox.
... debuggee is a messageport object that you can use to exchange messages with the debugger server.
...however, it can receive messages from the add-on that created it, and the add-on can pass it the debuggee so it can communicate with the debugger server the developer tools are targeting.
...And 6 more matches

Setting up an extension development environment - Archive of obsolete content
devtools.debugger.remote-enabled = true.
... this adds a "browser debugger" entry to the "web developer" submenu of the "tools" menu.
... the browser debugger can be used to debug the javascript code of extensions.
...And 5 more matches

Debug - Archive of obsolete content
the debug object is an instrinsic global object that sends output to a debugger.
... to debug internet explorer scripts, you must have a script debugger installed and the script must run in debug mode.
... internet explorer 8 and later versions include the javascript debugger.
...And 5 more matches

What are browser developer tools? - Learn web development
find out more find more out about the inspector in different browsers: firefox page inspector ie dom explorer chrome dom inspector (opera's inspector works the same as this) safari dom inspector and style explorer the javascript debugger the javascript debugger allows you to watch the value of variables and set breakpoints, places in your code that you want to pause execution and identify the problems that prevent your code from executing properly.
... to get to the debugger: firefox: select ➤ web developer ➤ debugger or press ctrl + shift + s to open the javascript debugger.
... if the tools are already displayed, click on the debugger tab.
...And 5 more matches

Tutorial: Show Allocations Per Call Path - Firefox Developer Tools
tutorial: show allocations per call path this page shows how to use the debugger api to show how many objects a web page allocates, sorted by the function call path that allocated them.
...(this menu will not be present unless you have changed the preference as explained above.) selecting the 'browser' context in the scratchpad enter the following code in the scratchpad: // this simply defines the 'debugger' constructor in this // scratchpad; it doesn't actually start debugging anything.
... components.utils.import('resource://gre/modules/jsdebugger.jsm'); adddebuggertoglobal(window); (function () { // the debugger we'll use to observe a tab's allocation.
...And 5 more matches

Chapter 6: Firefox extensions and XUL applications - Archive of obsolete content
venkman, the javascript debugger venkman is a full-fledged javascript debugger that runs inside firefox.
... it works like typical debuggers, and is useful not only for developing extensions, but also for general web development.
... also, because it works with the javascript in extensions and firefox itself, the debugger can be a good way to learn about design methods.
...And 4 more matches

Debugging JavaScript
browser debugger (built-in) on firefox 19 or later, it's possible to use the built-in js debugger on the browser itself.
... go to about:config and set the following two prefs: devtools.chrome.enabled: true devtools.debugger.remote-enabled: true after you restart the browser, you can access the browser debugger through tools > web developer > browser toolbox.
... (note that before firefox 28, this was labeled "browser debugger" and only the debugger was available, not the whole toolbox.) note that you must accept the incoming connection : (you may disable the pop-up above with the devtools.debugger.prompt-connection set to false in about:config.
...And 4 more matches

Debugging on Mac OS X
as a result, it is not possible to attach a debugger to these official firefox releases on macos 10.14+ without disabling system integrity protection (sip).
...a debugger can be attached to firefox processes of these builds.
... setting up lldb lldb is the debugger xcode provides/uses.
...And 4 more matches

How to get a stacktrace with WinDbg
(the keystroke for a pipe character on us keyboards is shift+\) submit the log file on a bug or via the support site, even if nothing seems to happen during the debug process start debugging now that firefox is opened in the debugger, you need to configure your windbg to download symbols from the mozilla symbol server.
...while firefox is running, you will not be able to type any commands into the debugger.
... if firefox fails to start, and you see lines of text followed by a command prompt in the debugger, a "breakpoint" may have been triggered.
...And 4 more matches

Tamarin build documentation - Archive of obsolete content
in the xcode project, this is the debug_debugger and release_debugger configurations.
... optional flags: --enable-debugger - debugger build --enable-debug - debug build for verbose build of tamarin, you can pass cppflags to make.
...for example, if you chose the win32 debug_debugger configuration your build will be under \tamarin-redux\platform\win32\obj_9\shell\debug_debugger by default.
...And 3 more matches

Debugging a XULRunner Application - Archive of obsolete content
browser debugger as of gecko 44, it is no longer possible to start the devtools server from xul apps.
... starting with xulrunner 24, you should use the firefox browser debugger to debug your xulrunner apps.
... add the following code to your xul app: components.utils.import('resource://gre/modules/devtools/dbg-server.jsm'); if (!debuggerserver.initialized) { debuggerserver.init(); // don't specify a window type parameter below if "navigator:browser" // is suitable for your app.
...And 3 more matches

Debug.write - Archive of obsolete content
the debug.write function sends strings to the script debugger.
..., strn optional strings to send to the script debugger.
... remarks the debug.write function sends strings to the immediate window of a script debugger at run time.
...And 3 more matches

Debug.writeln - Archive of obsolete content
the debug.writeln function sends strings to the script debugger, followed by a newline character.
..., strn optional strings to send to the script debugger.
... remarks the debug.writeln function sends strings, followed by a newline character, to the immediate window of the microsoft script debugger at run time.
...And 3 more matches

Handling common JavaScript problems - Learn web development
using the javascript debugger unfortunately, we still have the same error — the problem has not gone away.
... let's investigate this now, using a more sophisticated feature of browser developer tools: the javascript debugger as it is called in firefox.
... note: similar tools are available in other browsers; the sources tab in chrome, debugger in safari (see safari web development tools), etc.
...And 3 more matches

Shell global objects
this is what debugger.source.prototype.elementattributename returns.
...this is what debugger.source.prototype.elementattributename returns.
...if options is given, it may have any of the following properties: samezoneas the compartment will be in the same zone as the given object (defaults to a new zone) invisibletodebugger the global will be invisible to the debugger (default false) principal if present, its value converted to a number must be an integer that fits in 32 bits; use that as the new compartment's principal.
...And 3 more matches

Examine, modify, and watch variables - Firefox Developer Tools
this feature isn't yet supported in the new debugger.
... if you need to use it, you can, for now, switch back to the old debugger by visiting about:config and setting the "devtools.debugger.new-debugger-frontend" preference to false.
... to see the docs for the old debugger, please visit debugger (before firefox 52).
...And 3 more matches

Use watchpoints - Firefox Developer Tools
in the firefox debugger, this information can be provided by watchpoints.
... set a watchpoint run and then pause the debugger.
... in the scopes pane on the right side of the debugger user interface, find an object you want to watch, and right-click it to open its context menu.
...And 3 more matches

about:debugging (before Firefox 68) - Firefox Developer Tools
this page enables you to do two things: load an add-on temporarily from disk connect the add-on debugger to any restartless add-ons connecting the add-on debugger the add-ons page in about:debugging lists all restartless add-ons that are currently installed (note that this list may include add-ons that came preinstalled with your firefox).
...click "ok", and the add-on debugger will start in a separate window.
... note that sometimes the debugger window is hidden by the main firefox window.
...And 3 more matches

Migrate apps from Internet Explorer to Mozilla - Archive of obsolete content
venkman, shown in figure 3, is a powerful, cross-platform javascript debugger that integrates with mozilla.
... it is usually bundled with mozilla releases; you can find it at tools -> web development -> javascript debugger.
... for firefox, the debugger isn't bundled; instead, you can download and install it from the venkman project page.
...And 2 more matches

Remote debugging - Archive of obsolete content
the crash victim should at least know how to run a debugger, if not how to use it, and should have a debug build of firefox handy.
...it allows you to see the crash in a debugger even after the program has long exited.
...see here for instructions on how to do so with microsoft's free debugger, windbg.
...And 2 more matches

Table Layout Regression Tests - Archive of obsolete content
while the information on the layout debugger is still useful, the testing information is much less relevant now than it has been, as the "rtest" testing framework described here has been superseded by the reftest framework.
... to build the layoutdebugger itself, build either all extensions or include layoutdebug in your .mozconfig file.
... start the layout debugger via mozilla -layoutdebug - p foo where foo is just another profile than your main profile.
...And 2 more matches

Command line options
-jsdebugger start application with browser toolbox (formerly browser debugger).
... that is different to venkman debugger (see option -venkman).
... -start-debugger-server port firefox only.
...And 2 more matches

Hacking Tips
use the vixl debugger in the simulator (arm64) set a breakpoint (see the comments above about masm.breakpoint()) and run with the environment variable use_debugger=1.
... this will then drop you into a simple debugger provided with vixl, the arm simulator technology used for arm64 simulation.
... use the simulator debugger for arm32 the same instructions for arm64 in the preceeding section apply, but the environment variable differs: use arm_sim_debugger=1.
...And 2 more matches

Bytecode Descriptions
this is useful for the debugger and abstractgeneratorobject::isafteryieldorawait.
...however, the debugger still needs to be notified when control exits a scope; that's what this instruction does.
... debugger break in the debugger, if one is attached.
...And 2 more matches

SpiderMonkey Internals
there is an additional public api for javascript debuggers, jsdbgapi, but js/jsd/jsdebug.h might be a better api for debuggers.
...the debugger will have to consult jsopcode.def on its own to figure out where to plant trap instructions to implement functions like step out, but a future jsdbgapi.h will provide convenience interfaces to do these things.
... watchpoints, for intercepting set operations on properties and running a debugger-supplied function that receives the old value and a pointer to the new one, which it can use to modify the new value being set.
...And 2 more matches

Migrating from Firebug - Firefox Developer Tools
the network monitor can be opened via ctrl+shift+q / cmd+opt+q, the web console via ctrl+shift+k / cmd+opt+k and the debugger via ctrl+shift+s / cmd+opt+s.
...to stop the script execution there, you need to set a breakpoint on the line with the modification within the debugger panel.
... debugger what's the script panel in firebug, is the debugger panel in the devtools.
...And 2 more matches

Examine and edit HTML - Firefox Developer Tools
clicking the marker opens a tooltip listing the event listeners and allows you for each listener to switch to the line of javascript code in the debugger where the listener is defined.
...clicking the marker switches to the line of javascript code in the debugger where the custom element got defined.
... ::before and ::after you can inspect pseudo-elements added using ::before and ::after: custom element definition when you open the inspector on a page that includes custom elements, you can view the class definition for the custom element in the debugger: inspect the element click on the word custom the source for the element's class will be displayed in the debugger.
...And 2 more matches

Debugging Firefox Desktop - Firefox Developer Tools
in this guide, the instance of firefox being debugged is called the debuggee, and the instance of firefox doing the debugging is called the debugger.
... enable remote debugging first, you'll need to ensure that both debugger and debuggee have the "enable browser chrome and add-on debugging toolboxes" and "enable remote debugging" settings checked in the developer tools settings.
... start the debugger server next, you need to start the debugger server in the debuggee.
...And 2 more matches

about:debugging - Firefox Developer Tools
enter the location and port on which the debugger server is running.
... you can use the following buttons: inspect loads the extension in the debugger.
... note: it's recommended that you use the browser toolbox, not the add-on debugger, for debugging webextensions.
...And 2 more matches

Using gdb on wimpy computers - Archive of obsolete content
the debugger uses a lot of memory.
...[blizzard@gunhead bin]$ ./mozilla -g .//run-mozilla.sh -g ./mozilla-bin mozilla_five_home=/home/blizzard/src/mozilla/mozilla/dist/bin ld_library_path=/home/blizzard/src/mozilla/mozilla/dist/bin shlib_path=/home/blizzard/src/mozilla/mozilla/dist/bin libpath=/home/blizzard/src/mozilla/mozilla/dist/bin moz_program=./mozilla-bin moz_toolkit= moz_debug=1 moz_debugger= /usr/bin/gdb ./mozilla-bin -x /tmp/mozargs22288 gnu gdb 19991004 copyright 1998 free software foundation, inc.
...here's what it looks like in the 4.18 version of the debugger: ^c program received signal sigint, interrupt.
...(gdb) here's what it looks like in a version 5.x of the debugger ( yet unreleased ): ^c program received signal sigint, interrupt.

Debugging
debugging the mozilla platform using debuggers with mozilla debugging mozilla on windows faq questions (and answers) about debugging mozilla on windows.
... debugging mozilla with gdb gdb is our primary debugger on mac and linux.
... debugging mozilla with lldb lldb is the new debugger on mac.
... debugging mozilla with valgrind valgrind is a memory debugger for mac and linux.

JS_NewGlobalObject
hookoption js::onnewglobalhookoption see debugger api hook added in spidermonkey 31 options const js::compartmentoptions & the option for new compartment (passed to jscompartment constructor).
... debugger api hook during global creation, we fire notifications to callbacks registered via the debugger api.
... this api provides a way for consumers to set slots atomically (immediately after the global is created), before any debugger hooks are fired.
...this lets us be sure that debugger clients never miss breakpoints.

nsIEventListenerInfo
methods getdebugobject() returns the debugger object if the debug service is active.
...return value if jsdidebuggerservice is active and the listener is implemented in js, this returns the listener as a jsdivalue.
...this is the method you should use if you want to get access to the actual listener, but the debugger service must be already active, which significantly slows down script execution.
... accordingly, this should probably only be used by real debuggers.

Set watch expressions - Firefox Developer Tools
the debugger features a pane for entering expressions to be watched (watch expressions).
... as you step through code, the debugger will watch the expression and return any results.
... the debugger will save the expression and watch it as you step through your code.
... when the debugger reaches a breakpoint, it will display your watch expressions variables: you can step through your code, watching the value of the expression as it changes.

Settings - Firefox Developer Tools
debugger enable source maps enable source map support in the debugger.
... enable new debugger frontend enable the new debugger.
... enable worker debugging enable a panel within the debugger to debug workers.
... note: this option got removed from the ui in firefox 56, because this version ships with a new debugger ui, but it can still be enabled for the old ui by setting the preference devtools.debugger.workers to true.

cfx - Archive of obsolete content
this enables you to run your add-on alongside debuggers like firebug.
... for example, if you type: cfx run ---no-run you will see something like: to launch the application, enter the following command: /path/to/firefox/firefox-bin -profile /path/to/profile/tmpjdnlp6.mozrunner -foreground -no-remote this enables you to run the add-on without going through cfx, which might be useful if you want to run it inside a debugger like gdb.
... for example, if you type: cfx run ---no-run you will see something like: to launch the application, enter the following command: /path/to/firefox/firefox-bin -profile /path/to/profile/tmpjdnlp6.mozrunner -foreground -no-remote this enables you to run the add-on without going through cfx, which might be useful if you want to run it inside a debugger like gdb.

MMgc - Archive of obsolete content
(the second switch will slow your application down a lot more than the first switch, so you could try the first, then the second.) when a missing write barrier is detected, mmgc will assert and drop you into the debugger, and will print out a message telling you which object contained the missing write barrier, the address of the member variable that needs it, and what object didn't get marked due to the missing write barrier.
... the mmgc_memory_profiler feature is implied by the debugger feature and is always on in debug builds.
...if you're trying to see why memory is not getting reclaimed; gc::whospointingatme() can be called from the msvc debugger and will spit out objects that are pointing to the given memory location.

Remotely debugging Firefox for Metro - Archive of obsolete content
set up firefox for metro go to about:config in firefox for metro, and set the following required preference: devtools.debugger.remote-enabled = true you may also want to set these optional preferences: devtools.debugger.force-local = false (if you want to connect from a different machine over the network) devtools.debugger.remote-host (to change the tcp hostname where firefox will listen for connections) devtools.debugger.remote-port (to change the tcp port number where firefox will listen for connections) devtoo...
...ls.debugger.prompt-connection = false (allow connections without displaying a confirmation prompt.
...the toolbox will open in its own window, attached to the firefox for metro tab that's currently hosting mozilla.org: the toolbox, and the tools it hosts (including the console, debugger, style editor, profiler, etc.), work in just the same way as they do when attached to local content.

Venkman Internals - Archive of obsolete content
gijskruitbosch 05:41, 7 march 2007 (pst) venkman-debugger.js sets hooks in to the jsdidebuggerservice.
... initdebugger().
... scriptmanager in initdebugger() the previous loaded scripts are passed to an onscriptcreated() method which binds them to a scriptmanager.

Using Breakpoints in Venkman - Archive of obsolete content
basic breakpoints the stop button and debugger keyword are useful features of the javascript debugger, but when you are debugging deep in code—especially code you have authored yourself and are responsible for troubleshooting—you're going to need breakpoints.
...except for this distinction, breakpoints in venkman work like breakpoints in most other debuggers.
... using breakpoints to debug when you set a breakpoint, you give venkman (or whatever debugger you're using) the opportunity to display information about the execution environment.

Settings - Archive of obsolete content
the debugger has its own settings menu, which you can access from an icon in the toolbar: each setting is a simple on/off switch: auto prettify minified sources with this option enabled, the debugger will automatically detect minified js files and pretty-print them.
... show panes on startup when this option is enabled, the debugger's variables pane is visible when you first start the debugger.
... show original sources enabling this option will make the debugger use source maps, if they are available, to display the original source for code which has been combined, minified, or even compiled to javascript from a language like coffeescript.

Parser API
interface debuggerstatement <: statement { type: "debuggerstatement"; } a debugger statement.
... note: the debugger statement is new in ecmascript 5th edition, although spidermonkey has supported it for years.
... debuggerstatement([loc]) loc: sourcelocation returns: customstatement callback to produce a custom debugger statement node.

Index
176 ijsdebugger debugger, interfaces, interfaces:scriptable, xpcom interface reference implemented by: @mozilla.org/jsdebugger;1 as a service: 177 amiinstallcallback interfaces, interfaces:scriptable, xpcom, xpcom interface reference called when an install completes or fails.
...see the version_* consts on jsdidebuggerservice.
...eference, xpcom interface reference implemented by: @mozilla.org/process/environment;1 as a service: 586 nsierrorservice interfaces, interfaces:scriptable, needscontent, xpcom interface reference implemented by: @mozilla.org/xpcom/error-service;1 587 nsieventlistenerinfo interfaces, interfaces:scriptable, xpcom, xpcom interface reference returns the debugger object if the debug service is active.

jsdIStackFrame
js/jsd/idl/jsdidebuggerservice.idlscriptable please add a summary to this article.
...see the version_* consts on jsdidebuggerservice.
... isdebugger boolean true if stack frame represents a frame created as a result of a debugger evaluation.

nsIDebug
break() requests the software break into a debugger.
... if no debugger is running then this usually results in a program crash.
...this allows the debugger to be attached before the software break.

Browser Toolbox - Firefox Developer Tools
note: if you want to debug a specific add-on that is restartless or sdk-based then try the add-on debugger.
... you will be presented with a dialog like this (it can be removed by setting the devtools.debugger.prompt-connection property to false): click ok, and the browser toolbox will open in its own window: you'll be able to inspect the browser's chrome windows and see, and be able to debug, all the javascript files loaded by the browser itself and by any add-ons that are running.
... altogether you will have access to the following developer tools: debugger (note: if you want to debug a specific add-on that is restartless or sdk-based then try the add-on debugger.) console style editor performance network monitor page inspector accessibility inspector you can debug chrome: and about: pages using the normal debugger, just as if they were ordinary content pages.

Ignore a source - Firefox Developer Tools
however, you can tell the debugger to ignore the details of selected sources.
... when “pause on exceptions” is enabled in the debugger settings, the debugger won’t pause when an exception is thrown in the ignored source; instead it waits until (and if) the stack unwinds to a frame in a source that isn’t ignored.
... the debugger skips through ignored sources when stepping.

Step through code - Firefox Developer Tools
when the debugger is stopped at a breakpoint, you can step through it using four buttons in the toolbar: in order, the buttons are: play: run to the next breakpoint step over: advance to the next line in the same function.
... step in: advance to the next line in the function, unless on a function call, in which case enter the function being called step out: run to the end of the current function, in which case, the debugger will skip the return value from a function, returning execution to the caller split console when paused, you can press the esc key to open and close the split console to gain more insight into errors and variables: pause on breakpoints overlay since firefox 70, when your code is paused on a breakpoint an overlay appears on the viewport of the tab you are debugging.
... if you want to turn this feature off, since firefox 71 you can do so by going to about:config in a new tab, setting the devtools.debugger.features.overlay pref to false, and restarting the browser.

Use a source map - Firefox Developer Tools
a source map is a file that maps from the transformed source to the original source, enabling the browser to reconstruct the original source and present the reconstructed original in the debugger.
... to enable the debugger to work with a source map, you must: generate the source map include a comment in the transformed file, that points to the source map.
...the compiled source contains a comment like this, that points to a source map: //# sourcemappingurl=main.js.map in the debugger's source list pane, the original coffeescript source now appears as "main.coffee", and we can debug it just like any other source.

All keyboard shortcuts - Firefox Developer Tools
owser console ctrl + shift + j cmd + shift + j ctrl + shift + j open browser toolbox ctrl + alt + shift + i cmd + opt + shift + i ctrl + alt + shift + i open scratchpad shift + f4 shift + f4 * shift + f4 open webide shift + f8 shift + f8 * shift + f8 storage inspector shift + f9 shift + f9 * shift + f9 open debugger 3 ctrl + shift + z cmd + opt + z ctrl + shift + z 1.
... enter return enter debugger command windows macos linux close current file ctrl + w cmd + w ctrl + w search for a string in the current file ctrl + f cmd + f ctrl + f search for a string in all files ctrl + shift + f cmd + shift + f ctrl + shift + f find next in the current file ctrl + g cmd + g ctrl + g search for scripts b...
... note: before firefox 66, the combination ctrl + shift + s on windows and linux or cmd + opt + s on macos would open/close the debugger.

Release notes - Archive of obsolete content
add-on debugger now includes a console and a scratchpad.
... firefox 31 highlights add-on debugger added the ability to convert between high-level browserwindow objects and dom windows, and between high-level tab objects and xul tabs.

jpm - Archive of obsolete content
for example, to pass the -jsconsole argument to firefox and launch the browser console, try the following: jpm run --binary-args -jsconsole to pass multiple arguments, or arguments containing spaces, quote them: jpm run --binary-args '-url mzl.la -jsconsole' --debug run the add-on debugger attached to the add-on.
... for example, to pass the -jsconsole argument to firefox, which will launch the browser console, try the following: jpm test --binary-args -jsconsole to pass multiple arguments, or arguments containing spaces, quote them: jpm test --binary-args '-url mzl.la -jsconsole' --debug run the add-on debugger attached to the add-on.

Setting Up a Development Environment - Archive of obsolete content
javascript debugger the name says it all.
... the venkman javascript debugger is a great way to trace execution of your javascript code.

Environment variables affecting crash reporting - Archive of obsolete content
moz_crashreporter_fulldump store full application memory in the minidump, so you can open it in a microsoft debugger.
...you can use this if you would rather use the jit debugger on windows with the symbol server, for example.

Debug.setNonUserCodeExceptions - Archive of obsolete content
the debug.setnonusercodeexceptions property determines whether any try-catch blocks in this scope are to be treated by the debugger as user-unhandled.
... syntax debug.setnonusercodeexceptions [= bool]; remarks if this property is set to true within a given scope, the debugger can then choose whether to take some specified action on exceptions thrown inside that scope: for instance, if the developer wishes to break on user-unhandled exceptions.

Object.prototype.unwatch() - Archive of obsolete content
description the javascript debugger has functionality similar to that provided by this method, as well as other debugging options.
... for information on the debugger, see venkman.

Object.prototype.watch() - Archive of obsolete content
the javascript debugger has functionality similar to that provided by this method, as well as other debugging options.
... for information on the debugger, see venkman.

Capturing a minidump
capture a minidump connect firefox to the debugger.
...if the debugger spits out some text right away and firefox doesn't come up, select debug → go again.

Obsolete Build Caveats and Tips
alternatively you can install the command-line compiler as part of the windows 7 sdk, but you are then expected to use the included windbg debugger.
... the visual c++ 8 command-line compiler is included with the vista sdk, but you are then expected to use the included windbg debugger.

Profiling with the Firefox Profiler
set devtools.debugger.remote-enabled to true in about:config for fennec.
... native stack the native stack is the regular c / c++ / rust function stack that you know from your debugger.

JSDBGAPI
typedef jsstackframe js_frameiterator js_getframescript js_getframepc js_getscriptedcaller js_stackframeprincipals js_evalframeprincipals js_getframeannotation js_setframeannotation js_getframeprincipalarray js_isnativeframe js_getframeobject js_getframescopechain js_getframecallobject js_getframethis js_getframefunction js_getframefunctionobject js_isconstructorframe js_isdebuggerframe js_getframereturnvalue js_setframereturnvalue js_getframecalleeobject js_getscriptfilename js_getscriptbaselinenumber js_getscriptlineextent js_getscriptversion js_gettopscriptfilenameflags js_getscriptfilenameflags js_flagscriptfilenameprefix jsfilename_null jsfilename_system jsfilename_protected evaluating debug code js_evaluateinstackframe examining object pro...
...perties typedef jspropertydesc jspd_enumerate jspd_readonly jspd_permanent jspd_alias jspd_argument jspd_variable jspd_exception jspd_error typedef jspropertydescarray js_propertyiterator js_getpropertydesc js_getpropertydescarray js_putpropertydescarray hooks js_setdebuggerhandler js_setsourcehandler js_setexecutehook js_setcallhook js_setobjecthook js_setthrowhook js_setdebugerrorhook js_setnewscripthook js_setdestroyscripthook js_getglobaldebughooks js_setcontextdebughooks memory usage js_getobjecttotalsize js_getfunctiontotalsize js_getscripttotalsize system objects js_issystemobject js_newsystemobject profiling these functions can be used to profile a spidermonkey application using the mac profiler, shark.

Profiling SpiderMonkey
instructions 1.) get yourself an optimized libxul build of firefox, with debugger info.
...here's a sample mozconfig: mk_add_options moz_objdir=@topsrcdir@/ff-opt-libxul mk_add_options moz_make_flags=-j3 ac_add_options --enable-optimize ac_add_options --enable-libxul ac_add_options --enable-shark ac_add_options --enable-debugger-info-modules ac_add_options --enable-application=browser 2.) you'll want to run shark on both the browser and [xpcshell], since the host environments differ.

Exploitable crashes
a crash report from your debugger, your os, or mozilla crash-stats can tell you a lot about whether or not a crash is potentially exploitable.
...microsoft released a debugger extension tool in 2009 called "!exploitable".

Debugging service workers - Firefox Developer Tools
if this is not enough to help you figure out the problem, you could also try going to the javascript debugger and stepping through your code to pinpoint exactly where it is going wrong.
...when pressed, this takes you straight to the javascript debugger view of your service worker code, and you can use the full power of the debugger to debug it — stepping through code, etc.

Break on DOM mutation - Firefox Developer Tools
once you set the breakpoint, go to the debugger.
... when you execute the code, the debugger will pause execution when the dom mutation occurs.

Debug worker threads - Firefox Developer Tools
the debugger shows the source code for all running worker threads — web workers, service workers, etc.
... you can set a breakpoint (or logpoint) on any active worker thread: when execution is paused in a worker thread, the context of the debugger is updated to show the correct breakpoints, call stack, etc., just as you'd expect.

Access debugging in add-ons - Firefox Developer Tools
the following items are accessible in the context of chrome://browser/content/debugger.xul (or, in version 23 beta, chrome://browser/content/devtools/debugger.xul): window.addeventlistener("debugger:editorloaded") - called when the read-only script panel loaded.
... window.addeventlistener("debugger:editorunloaded") relevant files: chrome://browser/content/devtools/debugger-controller.js chrome://browser/content/devtools/debugger-toolbar.js chrome://browser/content/devtools/debugger-view.js chrome://browser/content/devtools/debugger-panes.js unfortunately there is not yet any api to evaluate watches/expressions within the debugged scope, or highlight elements on the page that are referenced as variables in the debugged scope.

Set a conditional breakpoint - Firefox Developer Tools
a normal breakpoint is just associated with a line: when the program reaches that line, the debugger pauses.
...when the program reaches the line, the debugger pauses only if the breakpoint's specified expression evaluates to true.

How to - Firefox Developer Tools
these articles describe how to use the debugger.
... access debugging in add-onsbreaking on exceptionsdebug eval sourcesdisable breakpointsexamine, modify, and watch variableshighlight and inspect dom nodesignore a sourceopen the debuggerpretty-print a minified filesearchset a breakpointset a conditional breakpointset watch expressionsstep through codeuse a source mapuse watchpoints ...

Set a logpoint - Firefox Developer Tools
to create a logpoint: right click on a line number in the debugger panel and pick add log action from the context menu.
...you can make it easier to see the message by opening a split console under the debugger.

Set event listener breakpoints - Firefox Developer Tools
starting with firefox 69, debugging an application that includes event handlers is simplified because the debugger now includes the ability to automatically break when the code hits an event handler.
... using a standard event breakpoint to use an event breakpoint, you open up the javascript debugger, and find and expand the event listener breakpoints section in the right hand column.

Source map errors - Firefox Developer Tools
you may encounter this when trying to open one of the original sources in the debugger.
... the message looks a little different in this case: in this case, the error will also be displayed in the source tab in the debugger: networkerror when attempting to fetch resource a bug in firefox prevents it from loading source maps for web extensions.

Deprecated tools - Firefox Developer Tools
canvas debugger bugzilla issue: bug 1403938 removed as of firefox 67 description canvas debugger allowed users to inspect the canvas element and see how frequently a given function is called.
... we do not have dedicated documentation for the canvas debugger.

DevTools API - Firefox Developer Tools
while this api is currently a work-in-progress, there are usable portions of page inspector and debugger that may be used currently.
...paused, inactive debugger).

Dominators view - Firefox Developer Tools
clicking the file name will take you to that spot in the debugger.
... using the call stack view finally, you can switch to the call stack view, see where the objects are being allocated, and jump to that point in the debugger: ...

Toolbox - Firefox Developer Tools
there are a few different ways to open the toolbox: select "toggle tools" from the web developer menu (under "tools" on os x and linux, or "firefox" on windows) click the wrench icon (), which is in the main toolbar or under the hamburger menu (), then select "toggle tools" activate any tool hosted in the toolbox (for example, the javascript debugger or the page inspector) press ctrl + shift + i on windows and linux, or cmd + opt + i on os x.
...the array may include the following tools: web console javascript debugger page inspector style editor profiler network monitor note that not all the hosted tools are always listed here: only the tools actually available in this context are shown (for example, not all tools support remote debugging yet, so if the debugging target is not the firefox instance that launched the window, not all the hosted tools will be shown).

Rich output - Firefox Developer Tools
the output will look something like this: console.log(todolist) array(4) [ {…}, {…}, {…}, {…} ] debugger eval code:1:9 undefined if you expand objects, such as arrays, you get slightly different content.
..."done", description: "morning pages", datecreated: 1552404478137 } ​ 1: object { status: "in progress", description: "refactor styles", datecreated: 1552404493169 } ​ 2: object { status: "to do", description: "create feedback form", datecreated: 1552404512630 } ​ 3: object { status: "to do", description: "normalize table", datecreated: 1552404533790 } ​ length: 4 ​ <prototype>: array [] debugger eval code:1:9 undefined highlighting and inspecting dom nodes if you hover the mouse over any dom element in the console output, it's highlighted on the page: in the screenshot above you'll also see a blue "target" icon next to the node in the console output: click it to switch to the inspector with that node selected.

Lexical grammar - JavaScript
keywords reserved keywords as of ecmascript 2015 break case catch class const continue debugger default delete do else export extends finally for function if import in instanceof new return super switch this throw try typeof var void while with yield future reserved keywords the following are reserved as future keywords by the ecmascript specification.
... `string text line 1 string text line 2` `string text ${expression} string text` tag `string text ${expression} string text` automatic semicolon insertion some javascript statements must be terminated with semicolons and are therefore affected by automatic semicolon insertion (asi): empty statement let, const, variable statement import, export, module declaration expression statement debugger continue, break, throw return the ecmascript specification mentions three rules of semicolon insertion.

XPath
xmlquire (formerly known as sketchpath) a graphical xpath builder/debugger(.net).
... xpath tester an online xpath builder/debugger.

Using the WebAssembly JavaScript API - WebAssembly
the equivalent code would look like this: fetch('simple.wasm').then(response => response.arraybuffer() ).then(bytes => webassembly.instantiate(bytes, importobject) ).then(results => { results.instance.exports.exported_func(); }); viewing wasm in developer tools in firefox 54+, the developer tool debugger panel has functionality to expose the text representation of any wasm code included in a web page.
... to view it, you can go to the debugger panel and click on the “wasm://” entry.

simple-storage - Archive of obsolete content
accessing storage from the console in the add-on debugger, you can access your add-on's simple-storage programmatically from the console using the following: loader.modules['resource://gre/modules/commonjs/sdk/simple-storage.js'].exports.storage clarification from mozilla needed: writing the above line in add-on debugger console results in "referenceerror: loader is not defined".

Tutorials - Archive of obsolete content
add-on debugger debug your add-on's javascript.

Bootstrapped extensions - Archive of obsolete content
add-on debugger from firefox 31 onwards, you can use the add-on debugger to debug bootstrapped add-ons.

Code snippets - Archive of obsolete content
downloading files code to download files, images, and to monitor download progress password manager code used to read and write passwords to/from the integrated password manager bookmarks code used to read and write bookmarks javascript debugger service code used to interact with the javascript debugger service svg general general information and utilities svg animation animate svg using javascript and smil svg interacting with script using javascript and dom events to create interactive svg embedding svg in html and xul using svg to enhance html or xul based markup xul widgets html in xul for rich tooltips dynamically...

Appendix D: Loading Scripts - Archive of obsolete content
debugging: jsd knows nothing about workers and no javascript debuggers work on them.

Local Storage - Archive of obsolete content
any extension that is more complex than a hello world needs some way to log errors and trace execution without having to fire up a debugger.

Index of archived content - Archive of obsolete content
ution dialogs and prompts downloading files drag & drop embedding svg examples and demos from articles file i/o finding window handles forms related code snippets html in xul for rich tooltips html to dom isdefaultnamespace js xpcom javascript debugger service javascript timers javascript daemons management label and description lookupnamespaceuri lookupprefix miscellaneous modules on page load page loading post data to window preferences progress...

List of Mozilla-Based Applications - Archive of obsolete content
ylizer css editor css editor css editor with built-in firebug-like diagnostics and gecko 1.8 preview sun java enterprise system server products uses nss sundial browser with advanced domain name technology based on firefox surfeasy private and secure web browsing sweet16 apple ii computer emulator uses spidermonkey as a scriptable debugger for software running in the emulator mozilla sunbird/mozilla lightning calendar tabpress authoring tool talend open studo data integration software seems to use xulrunner talking clipboard text to speech software read epub books, web pages, chm, pdf, ms word, rtf, rss feeds taskpool productivity telasocial k...

MCD, Mission Control Desktop, AKA AutoConfig - Archive of obsolete content
needed to patch and recompile that source rpm (check bug 295329) ; patch: [root@b008-02 sources]# cat thunderbird-autoconfigandldap.patch diff -ur thunderbird-3.0/configure thunderbird-3.0.autoldap/configure --- thunderbird-3.0/configure 2009-06-29 11:37:21.677372297 +0200 +++ thunderbird-3.0.autoldap/configure 2009-06-29 14:41:11.547435040 +0200 @@ -12855,7 +12855,7 @@ moz_feeds=1 moz_jsdebugger=1 moz_jsloader=1 -moz_ldap_xpcom= +moz_ldap_xpcom=1 moz_mail_news= moz_mork=1 moz_morkreader= and set --enable-extensions=pref in mozconfig file, in fedora source rpm it is: [root@b008-02 sources]# grep enable-extensions /root/rpmbuild/sources/thunderbird-mozconfig ac_add_options --enable-extensions=pref it seems worse this time , as even after applying those compilation options mentione...

Source code directories overview - Archive of obsolete content
these include: cookies, irc, wallet, dom inspector, p3p, schema validation, spellchecker, transformiix, typeaheadfind, javascript debugger, xforms, etc.

Mozilla Application Framework - Archive of obsolete content
tools venkman a javascript debugger with support for breakpoints, conditional breakpoints, local variable inspection, watch variables, single step, stop on error, profile data collection, report generation, code reformatting (pretty printing), and more.

Abc Assembler Tests - Archive of obsolete content
y summary end():void - test section finished compare_stricteq(name:string, expected:*, actual:*):void - compare the results of a testcase where name is the testcase name compare_typeerror(name:string, expected:*, actual:*):void - special function for comparing typeerrors (runtimeerrors) - will only compare the first 22 chars of expected and actual so that test can be run in release and releasedebugger configurations.

Actionscript Acceptance Tests - Archive of obsolete content
the first line must contain the expected error (without the extra debugger information).

Cmdline tests - Archive of obsolete content
two use cases for the cmdline testsuite: use case 1: test the interactive cmdline debugger test contents: start avmshell -d test.abc, set breakpoint on a line, show local variable value, quit from cmdutils import * def run(): r=runtestlib() r.run_test( 'debugger locals', '%s -d testdata/debug.abc'%r.avmrd, input='break 53\ncontinue\nnext\ninfo locals\nnext\ninfo locals\nquit\n', expectedout=['local1 = undefined','local2 = 10','local2 = 15'] ) use case 2: test -memstats returns ...

Running Tamarin acceptance tests - Archive of obsolete content
for each test run regardless of results, then print the test run summary when finished --ascargs= : additional arguments to pass to asc.jar --vmargs= : additional arguments to pass to avmshell --random : run tests in random order --timeout : max time for testrun --verify : run a verify pass instead of running abcs --verifyonly : run a -dverifyonly pass: only checks test exitcode (only works with debugger vms) testing the android shell the instructions above apply to running tests on an android device as well, but with a few differences.

Tamarin Acceptance Testing - Archive of obsolete content
successfully build release and debug versions of the shell with the debugger enabled [info] successfully run the following test suites: acceptance test suite [info] self tests [info] submit a sandbox build request to test against platforms that you may not have locally [info] available tamarin acceptance test suites actionscript acceptance tests: actionscript acceptance tests running tamarin acceptance tests abc assembler tests cmdline tests performance tests actionscript performance tests running tamarin performance tests built-in self tests ...

Tamarin Build System Documentation - Archive of obsolete content
the acceptance tests are the majority and are run on all shells (release, release-debugger, debug, debug-debugger).

Archived Mozilla and build documentation - Archive of obsolete content
venkman venkman is the code name for mozilla's javascript debugger.

2006-11-17 - Archive of obsolete content
two questions: (1) launching a separate intance of firefox.exe, and (2) programmatically closing a window user has two questions about using adobe flex builder debugger in firefox 2.0.

Extentsions FAQ - Archive of obsolete content
use the debugger by typing in a command like this: /break chrome://myextension/content/myfile.js 123 then i suggest using flat chrome.

2006-12-01 - Archive of obsolete content
a tip on how to debug firefox extensions using a debugger.

Tamarin Tracing Build Documentation - Archive of obsolete content
in the xcode project, this is the debug_debugger and release_debugger configurations.

Common Firefox theme issues and solutions - Archive of obsolete content
debugger debugger toolbar buttons are missing icons on the debugger (tools > web developer > debugger) the toolbar buttons are missing their icons.

Debug.msTraceAsyncCallbackStarting - Archive of obsolete content
note: some debugging tools do not display the information sent to the debugger.

Debug.msTraceAsyncCallbackCompleted - Archive of obsolete content
the possible values for status include: debug.ms_async_op_status_success debug.ms_async_op_status_canceled debug.ms_async_op_status_error note: some debugging tools do not display the information sent to the debugger.

Debug.msUpdateAsyncCallbackRelation - Archive of obsolete content
note: some debugging tools do not display the information sent to the debugger by this function.

Visual typescript game engine - Game development
luanch debugger configuration comes with this project.

IDE - MDN Web Docs Glossary: Definitions of Web-related terms
an ide normally consists of a source code editor, build automation tools and a debugger.

Index - MDN Web Docs Glossary: Definitions of Web-related terms
an ide normally consists of a source code editor, build automation tools and a debugger.

What went wrong? Troubleshooting JavaScript - Learn web development
the name of the javascript file, which links through to the debugger tab of the developer tools.

Server-side web frameworks - Learn web development
it contains a development server and debugger, and includes support for jinja2 templating, secure cookies, unit testing, and restful request dispatching.

Ember resources and troubleshooting - Learn web development
both of these files are generated with sourcemaps, so when you open the vendor.js or {app-name}.js to search for relevant code, when a debugger is placed, the sourcemap will be loaded and the breakpoint will be placed in the pre-transpiled code for easier correlation to your project code.

Browser chrome tests
for example, to run the tests in browser/base/content/test the command would be: ./mach mochitest -f browser browser/base/content/test/ or without mach test_path=<path_to_the_tests> make -c <objdir> mochitest-browser-chrome to run tests in debugger the following should work ./mach mochitest -f browser --debugger gdb browser/base/content/test/ run ./mach help mochitest-browser for more options.

Configuring Build Options
this makes it much easier to step through code in a debugger.

Eclipse CDT
that done, open the workspace preferences, select "c/c++ > debug > gdb", and set "gdb debugger" to the full path of your new gdb executable.

mach
if it works, you can look at compiler warnings: $ ./mach warnings-list try running the program: $ ./mach run try running your program in a debugger: $ ./mach run --debug try running some tests: $ ./mach xpcshell-test services/common/tests/unit/ or run an individual test: $ ./mach mochitest browser/base/content/test/general/browser_pinnedtabs.js you run mach from the source directory, so you should be able to use your shell's tab completion to tab-complete paths to tests.

Tracking Protection
note that with firefox for android, you can access console output using the remote debugger.

Geckoview-Junit Tests
@test fun contentcrashignored() { // cannot test x86 debug builds due to gecko's "ah_crap_handler" // that waits for debugger to attach during a sigsegv.

How to Report a Hung Firefox
instead of crashing firefox, more advanced developers who know how to use a debugger can try attaching to the firefox process and debugging in place.

Examples
sful and reason was = "' + asuccessreason + '"'); }, function(arejectreason) { alert('mypromise failed for reason = "' + uneval(arejectreason) + '"'); } ); function myuserdefinedpromise() { return 'i didnt do a promise.resolve so this will not understand that mypromise is a promise'; } // creates this error: /* exception: mypromise.then is not a function @scratchpad/5:8:1 wca_evalwithdebugger@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/devtools/server/actors/webconsole.js:1069:7 wca_onevaluatejs@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/devtools/server/actors/webconsole.js:734:9 dsc_onpacket@resource://gre/modules/commonjs/toolkit/loader.js -> resource://gre/modules/devtools/server/main.js:1098:9 ldt_send/<@resource://g...

Promise
to help with debugging, only when inspecting a promise object manually, you can see more information as special properties that are inaccessible from code (this, at present, is implemented by randomizing the property name, for the lack of more sophisticated language or debugger support).

source-editor.jsm
note: implementing actual support for debugger features such as breakpoints is up to you.

Mozilla projects on GitHub
debugger.html the debugger.html, a modern universal js debugger for firefox devtools, node, and every other js environment.

NSPR LOG FILE
this value causes logging output to be written using the windows function outputdebugstring(), which writes to the debugger window.

PR_Abort
syntax #include <prinit.h> void pr_abort(void); description pr_abort results in a core file and a call to the debugger or equivalent, in addition to causing the entire process to stop.

Rhino documentation
javascript debugger debugging scripts running in rhino.

Rhino license
license for portions of the rhino debugger additionally, some files (currently the contents of toolsrc/org/mozilla/javascript/tools/debugger/treetable/) are available under the following license: * copyright 1997, 1998 sun microsystems, inc.

Rhino overview
rhino contains all the features of javascript 1.7 allows direct scripting of java a javascript shell for executing javascript scripts a javascript compiler to transform javascript source files into java class files a javascript debugger for scripts executed with rhino language the javascript language itself is standardized by standard ecma-262 ecmascript: a general purpose, cross-platform programming language.

Index
518 parser api api, guide, javascript, spidermonkey example: 519 profiling spidermonkey guide 1.) get yourself an optimized libxul build of firefox, with debugger info.

JIT Optimization Outcomes
the interpreted callee function is being debugged by the debugger api.

JS::CompileOptions
the following are used in js shell: "js shell file" "js shell interactive" "js shell load" "js shell evaluate" "js shell run" "js shell disfile" "js shell compfile" "js shell parse" "js shell syntaxparse" "js shell offthreadcompilescript" and the following are used in self-hosted code and debugger: "self-hosted" "debugger eval" introductionlineno unsigned line number in the source code which introduces this source code.

JSFastNative
however, it causes the function not to appear on the stack in javascript debuggers.

JSNative
this causes the function not to appear on the stack in javascript debuggers.

JSObjectPrincipalsFinder
the two debugger functions js_stackframeprincipals and js_evalframeprincipals also use this callback.

JS_Add*Root
js_dumpnamedroots can be used to access this information from a debugger.

JS_SetFunctionCallback
note that debuggers should probably use js_setcallhook in preference to this function, because it is invoked when the javascript stack is guaranteed to be in a consistent state (and therefore it is valid to inspect and modify local variables, generate stack traces, and set breakpoints.) callback syntax typedef void (* jsfunctioncallback)(const jsfunction *fun,const jsscript *scr, const jsco...

Running Automated JavaScript Tests
u are not changing language-level functionality, you may wish to use jstests.py path_to_js_shell --exclude=test262 other options allow you to show the test command lines being run, command output and return codes, run tests named in a given file, exclude tests named in a given file, hide the progress bar, change the timeout, run skipped tests, print output in tinderbox format, run a test in the debugger, or run tests in valgrind.

SpiderMonkey: The Mozilla JavaScript runtime
js debugger api reference api reference for the debugger object introduced in spidermonkey 1.8.6, which corresponds to gecko 8.0 (firefox 8.0 / thunderbird 8.0 / seamonkey 2.5).

nsIEventListenerService
content/events/public/nsieventlistenerservice.idlscriptable a service that can be used to get a list of listeners observing events; this is primarily useful for debuggers.

nsIHttpActivityDistributor
this is primarily useful for debuggers and other traffic monitoring tasks.

nsIXPConnect
this is because we currently activate debugmode on all scripts in the jsruntime when the debugger is activated.

XPCOM Interface Reference
component; nsiprefbranchextensionmanager (toolkit)iaccessible2iaccessibleactioniaccessibleapplicationiaccessiblecomponentiaccessibleeditabletextiaccessiblehyperlinkiaccessiblehypertextiaccessibleimageiaccessiblerelationiaccessibletableiaccessibletable2iaccessibletablecelliaccessibletextiaccessiblevalueidispatchijsdebuggeramiinstallcallbackamiinstalltriggeramiwebinstallinfoamiwebinstalllisteneramiwebinstallpromptamiwebinstallerimgicacheimgicontainerimgicontainerobserverimgidecoderimgidecoderobserverimgiencoderimgiloaderimgirequestinidomutilsjsdistackframemoziasyncfaviconsmoziasynchistorymozicoloranalyzermozijssubscriptloadermozipersonaldictionarymoziplaceinfomoziplacesautocompletemoziregistrymozirepresentativecolor...

Reference Manual
this allows source level debuggers to more easily "follow" the pointer.

Using the Mozilla symbol server
the debugger will not be able to show you the content of all variables and the execution path can seem strange because of inlining, tail calls, and other compiler optimizations.

Introduction to DOM Inspector - Firefox Developer Tools
used in concert with mozilla tools like venkman, the javascript debugger, the dom inspector can give you a complete view of any web page or dom-based application interface.

Breaking on exceptions - Firefox Developer Tools
to instruct the debugger to pause on an exception, tick these checkboxes in the breakpoints list: pause on exceptions pause on caught exceptions when an exception occurs, the line where it occurs is highlighted in the source pane, with a squiggly red line under the problematic code.

Debug eval sources - Firefox Developer Tools
the debugger will also stop at debugger; statements in unnamed eval sources.

Highlight and inspect DOM nodes - Firefox Developer Tools
when you are working with dom notes in the debugger, you can easily highlight the node on the page or view it in the page inspector.

Pretty-print a minified file - Firefox Developer Tools
the debugger formats the source and displays it as a new file with a name like: "{ } [original-name]".

Search - Firefox Developer Tools
the debugger will display the number of matches in the code and highlight each result: using the outline tab if you are searching for a specific function within the current javascript file, you can use the outline tab in the debugger to find it quickly.

Set a breakpoint - Firefox Developer Tools
there are many different types of breakpoint that can be set in the debugger; this article covers standard (unconditional) breakpoints and conditional breakpoints.

Set an XHR breakpoint - Firefox Developer Tools
to turn on the feature: open the debugger click on "pause on any url" which acts as a wild card, causing the code to pause on any call, or, click the plus sign next to the xhr breakpoints header, enter the url in which you are interested, and press enter.

Aggregate view - Firefox Developer Tools
the file name and line number is a link: if we click it, we go directly to that line in the debugger: inverted call stack the call stack view is top-down: it shows allocations that happen at that point or points deeper in the call tree.

Examine Event Listeners - Firefox Developer Tools
ows the word "event" next to elements in the html pane, that have event listeners bound to them: click the icon, then you'll see a popup listing all the event listeners bound to this element: each line contains: a right-pointing arrowhead; click to expand the row and show the listener function source code a curved arrow pointing to a stack; click it to show the code for the handler in the debugger the name of the event for which a handler was attached to this element the name and line number for the listener; you can also click here to expand the row and view the listener function source code a label indicating whether the event bubbles a label indicating the system that defines the event.

Tips - Firefox Developer Tools
debugger skip javascript libraries in debugging sessions via the black box icon ().

Console messages - Firefox Developer Tools
click the link to open the file in the debugger.

Split console - Firefox Developer Tools
as usual, $0 works as a shorthand for the element currently selected in the inspector: when you use the split console with the debugger, the console's scope is the currently executing stack frame.

Working with iframes - Firefox Developer Tools
if you select an entry in the list, all the tools in the toolbox - the inspector, the console, the debugger and so on - will now target only that iframe, and will essentially behave as if the rest of the page does not exist.

Firefox Developer Tools
javascript debugger stop, step through, examine, and modify the javascript running in a page.

Event.currentTarget - Web APIs
instead, you can either directly console.log(event.currenttarget) to be able to view it in the console or use the debugger statement, which will pause the execution of your code thus showing you the value of event.currenttarget.

Index - HTTP
102 sourcemap http, http header, reference, response header, header the sourcemap http response header links generated code to a source map, enabling the browser to reconstruct the original source and present the reconstructed original in the debugger.

SourceMap - HTTP
the sourcemap http response header links generated code to a source map, enabling the browser to reconstruct the original source and present the reconstructed original in the debugger.

HTTP Index - HTTP
183 sourcemap http, http header, reference, response header, header the sourcemap http response header links generated code to a source map, enabling the browser to reconstruct the original source and present the reconstructed original in the debugger.

A re-introduction to JavaScript (JS tutorial) - JavaScript
the name also shows up in the debugger and some stack traces, which can save you time when debugging.

Functions - JavaScript
providing a name allows the function to refer to itself, and also makes it easier to identify the function in a debugger's stack traces: const factorial = function fac(n) { return n < 2 ?

Regular expressions - JavaScript
regex tester an online regex builder/debugger regex visualizer an online visual regex tester.

Memory Management - JavaScript
v8 engine flags the max amount of available heap memory can be increased with a flag: node --max-old-space-size=6000 index.js we can also expose the garbage collector for debugging memory issues using a flag and the chrome debugger: node --expose-gc --inspect index.js see also ibm article on "memory leak patterns in javascript" (2007) kangax article on how to register event handler and avoid memory leaks (2010) performance ...

Warning: -file- is being assigned a //# sourceMappingURL, but already has one - JavaScript
with source maps, the debugger can map the code being executed to the original source files.

SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. Use //# instead - JavaScript
with source maps, the debugger can map the code being executed to the original source files.

SyntaxError: missing variable name - JavaScript
sorry :( var debugger = "whoop"; // syntaxerror: missing variable name declaring multiple variables pay special attention to commas when declaring multiple variables.

Error.prototype.stack - JavaScript
see also debug eval sources in the debugger docs and this blog post.

Error.prototype.fileName - JavaScript
if called from a debugger context, the firefox developer tools for example, "debugger eval code" is returned.

SyntaxError() constructor - JavaScript
', 'somefile.js', 10); } catch (e) { console.error(e instanceof syntaxerror); // true console.error(e.message); // hello console.error(e.name); // syntaxerror console.error(e.filename); // somefile.js console.error(e.linenumber); // 10 console.error(e.columnnumber); // 0 console.error(e.stack); // @debugger eval code:3:9 } specifications specification ecmascript (ecma-262)the definition of 'nativeerror constructor' in that specification.

SyntaxError - JavaScript
', 'somefile.js', 10); } catch (e) { console.error(e instanceof syntaxerror); // true console.error(e.message); // hello console.error(e.name); // syntaxerror console.error(e.filename); // somefile.js console.error(e.linenumber); // 10 console.error(e.columnnumber); // 0 console.error(e.stack); // @debugger eval code:3:9 } specifications specification ecmascript (ecma-262)the definition of 'syntaxerror' in that specification.

Statements and declarations - JavaScript
others debugger invokes any available debugging functionality.

JavaScript reference - JavaScript
y.runtimeerror statements javascript statements and declarations control flowblock break continue empty if...else switch throw try...catch declarations var let const functions and classes function function* async function return class iterations do...while for for each...in for...in for...of for await...of while other debugger import label with expressions and operators javascript expressions and operators.

JavaScript
firefox developer tools web console, javascript profiler, debugger, and more.

XML introduction - XML: Extensible Markup Language
most browsers offer a debugger that can identify poorly-formed xml documents.