Event: timeStamp property
The timeStamp
read-only property of the
Event
interface returns the time (in milliseconds) at which the event was
created.
Value
This value is the number of milliseconds elapsed from the beginning of the time origin until the event was created. If the global object is Window
, the time origin is the moment the user clicked on the link, or the script that initiated the loading of the document. In a worker, the time origin is the moment of creation of the worker.
The value is a DOMHighResTimeStamp
accurate to
5 microseconds (0.005 ms), but the precision is reduced to prevent fingerprinting.
Example
HTML
html
<p>
Focus this iframe and press any key to get the current timestamp for the
keypress event.
</p>
<p>timeStamp: <span id="time">-</span></p>
JavaScript
js
function getTime(event) {
const time = document.getElementById("time");
time.firstChild.nodeValue = event.timeStamp;
}
document.body.addEventListener("keypress", getTime);
Result
Reduced time precision
To offer protection against timing attacks and fingerprinting, the precision of
Event.timeStamp
might get rounded depending on browser settings.
In Firefox, the privacy.reduceTimerPrecision
preference is enabled by
default and defaults to 2ms.
js
// reduced time precision (2ms) in Firefox 60
event.timeStamp;
// 1519211809934
// 1519211810362
// 1519211811670
// …
// reduced time precision with `privacy.resistFingerprinting` enabled
event.timeStamp;
// 1519129853500
// 1519129858900
// 1519129864400
// …
In Firefox, if you also enable privacy.resistFingerprinting
, the precision
will be 100ms or the value of
privacy.resistFingerprinting.reduceTimerPrecision.microseconds
, whichever
is larger.
Specifications
Specification |
---|
DOM Standard # ref-for-dom-event-timestamp① |
Browser compatibility
BCD tables only load in the browser