The lastModified
property of the Document
interface returns a string containing the date and time on which the current document was last modified.
Syntax
var string = document.lastModified;
Examples
Simple usage
This example alerts the value of lastModified
.
alert(document.lastModified); // returns: Tuesday, December 16, 2017 11:09:42
Transforming lastModified into a Date object
This example transforms lastModified
into a Date
object.
let oLastModif = new Date(document.lastModified);
Transforming lastModified into milliseconds
This example transforms lastModified
into the number of milliseconds since January 1, 1970, 00:00:00, local time.
let nLastModif = Date.parse(document.lastModified);
Notes
Note that as a string, lastModified
cannot easily be used for comparing the modification dates of documents. Here is a possible example of how to show an alert message when the page changes (see also: JavaScript cookies API):
if (Date.parse(document.lastModified) > parseFloat(document.cookie.replace(/(?:(?:^|.*;)\s*last_modif\s*\=\s*([^;]*).*$)|^.*$/, "$1") || "0")) { document.cookie = "last_modif=" + Date.now() + "; expires=Fri, 31 Dec 9999 23:59:59 GMT; path=" + location.pathname; alert("This page has changed!"); }
β¦the same example, but skipping the first visit:
var nLastVisit = parseFloat(document.cookie.replace(/(?:(?:^|.*;)\s*last_modif\s*\=\s*([^;]*).*$)|^.*$/, "$1")), nLastModif = Date.parse(document.lastModified); if (isNaN(nLastVisit) || nLastModif > nLastVisit) { document.cookie = "last_modif=" + Date.now() + "; expires=Fri, 31 Dec 9999 23:59:59 GMT; path=" + location.pathname; if (isFinite(nLastVisit)) { alert("This page has been changed!"); } }
If you want to know whether an external page has changed, please read this paragraph about the XMLHttpRequest()
API.
Specifications
Specification | Status | Comment |
---|---|---|
HTML Living Standard The definition of 'document.lastModified' in that specification. |
Living Standard |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
lastModified | Chrome Full support 1 | Edge Full support 12 | Firefox Full support Yes | IE ? | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Firefox Android Full support Yes | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes |
Legend
- Full support
- Full support
- Compatibility unknown
- Compatibility unknown