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Returns a string containing the date and time on which the current document was last modified.

Syntax

string = document.lastModified; 

Example

Example #1: Simple usage

alert(document.lastModified); 
// returns: Tuesday, July 10, 2001 10:19:42

Example #2: Transforming lastModified into a Date object

var oLastModif = new Date(document.lastModified);

Example #3: Transforming lastModified into number of milliseconds since January 1, 1970, 00:00:00, local time.

var nLastModif = Date.parse(document.lastModified);

Notes

Note that as a string, lastModified cannot easily be used for comparisons between the modified 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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes ? Yes ? ? ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes ? Yes ? ? ?

See also

Etiquetas y colaboradores del documento

Última actualización por: fscholz,