document.lastModified

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!");
    }
}

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

Specification

HTML5

See also

• MSDN: lastModified Property