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*([^;]*).*$)|^.*$/, "$1") || "0")) {
document.cookie = "last_modif=" + Date.now() + "; expires=Fri, 31 Dec 9999 23:59:59 GMT; path=" + location.pathname;
alert("This page has changed!");
}
…the same example, but skipping the first visit:
var
nLastVisit = parseFloat(document.cookie.replace(/(?:(?:^|.*;)\s*last_modif\s*\=\s*([^;]*).*$)|^.*$/, "$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
BCD tables only load in the browser