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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!");
  }
}
Note: WebKit returns the time string in UTC; Gecko and Internet Explorer return a time in the local timezone. (See: Bug 4363 – document.lastModified returns date in UTC time, but should return it in local time)

If you want to know whether an external page has changed, please read this paragraph about the XMLHttpRequest() API.

Specification

HTML5

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
lastModifiedChrome Full support 1Edge Full support 12Firefox Full support YesIE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

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