Date.now() - JavaScript | MDN
source link: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/now
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Date.now()
The static Date.now() method returns the number of
milliseconds elapsed since January 1, 1970 00:00:00 UTC.
Syntax
Date.now()
Return value
A Number representing the milliseconds elapsed since the UNIX epoch.
Polyfill
This method was standardized in ECMA-262 5th edition. Engines which have not been updated to support this method can work around the absence of this method using the following shim:
if (!Date.now) {
Date.now = function now() {
return new Date().getTime();
};
}
Examples
Reduced time precision
To offer protection against timing attacks and fingerprinting, the precision of
Date.now() might get rounded depending on browser settings.
In Firefox, the privacy.reduceTimerPrecision preference is enabled by
default and defaults to 20µs in Firefox 59; in 60 it will be 2ms.
// reduced time precision (2ms) in Firefox 60
Date.now()
// 1519211809934
// 1519211810362
// 1519211811670
// ...
// reduced time precision with `privacy.resistFingerprinting` enabled
Date.now();
// 1519129853500
// 1519129858900
// 1519129864400
// ...
In Firefox, you can also enable privacy.resistFingerprinting, the
precision will be 100ms or the value of
privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever
is larger.
Specifications
SpecificationECMAScript Language Specification (ECMAScript)# sec-date.now
Browser compatibility
Report problems with this compatibility data on GitHubdesktopmobileserverChromeEdgeFirefoxInternet ExplorerOperaSafariWebView AndroidChrome AndroidFirefox for AndroidOpera AndroidSafari on iOSSamsung InternetDenoNode.jsnowLegend
See also
- A polyfill of
Date.nowis available incore-js -
Performance.now()— provides timestamps with sub-millisecond resolution for use in measuring web page performance console.time()/console.timeEnd()
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