requestAnimationFrame: what exactly is the timestamp?

Question

I have always thought that timestamp used by requestAnimationFrame is the same as usual timestamp in JavaScript, that is number of milliseconds since January 1st, 1970. Today I

Answer 1

Finally, I found the answer in an article by Paul Irish and the specification of High Resolution time:

requestAnimationFrame API: now with sub-millisecond precision

High Resolution Time

The rAF time is "measured relative to the start of navigation of the document", that is relative to the "navigationStart attribute of the PerformanceTiming interface".

Answer 2

It's a DOMHighResTimeStamp or a high-resolution timestamp (the same you get with window.performance.now()).

The time stamp is:

current time for when requestAnimationFrame starts to fire callbacks.

The main difference between an ordinary timestamp and high-res timestamp is:

DOMTimeStamp only has millisecond precision, but DOMHighResTimeStamp has a minimal precision of ten microseconds.

Note: some browsers do not implement this aspect of rAF yet and may give you faulty or no value as argument.

Some resources:

• requestAnimationFrame
• DOMHighResTimeStamp

Answer 3

MDN says:

The callback has one single argument, a DOMHighResTimeStamp, which indicates the current time (the time returned from performance.now() )

And this is what performance.now() returns:

The returned value represents the time elapsed since the time origin.

The time origin is a standard time which is considered to be the beginning of the current document's lifetime.