This comment was originally written by @bp74

Maybe it's important to add that this is on a Windows 7 64 bit machine.

This comment was originally written by @bp74

Okay i did some more tests, dependent on the browser you get different results:

IE 9: error because performance.now() does not exist.
IE 10: microsecond precision (!!!)
Dartium: millisecond precision
Chrome 26: millisecond precision
Chrome 28.0.1458.0: millisecond precision
Firefox 19: microsecond precision (!!!)

So only IE10 and Firefox 19 work as expected (on Windows 7) but not WebKit browsers.

cc @blois.
Added Area-HTML, C2, Triaged labels.

Not quite sure I follow-
I'm seeing microsecond resolution from Stopwatch in Dartium and millisecond resolution from Stopwatch in all dart2js.

I'm seeing window.performance.now as microseconds in all supported cases.

Is the request that Stopwatch use window.performance.now in dart2js when possible?

This comment was originally written by @bp74

If you call window.performance.now() several times, you get this times:
216.999999996915
182.99999999726424
167.00000000128057
198.00000000395812
199.00000000052387

the now() function should give you milliseconds but with a microsecond resolution. The problem is that it does not give you the fraction of the millisecond. The fraction is always 000 or 999.

The same happens with a Stopwatch. The Stopwatch class has a "microseconds" property, but the value is always a multiple of 1000.

This comment was originally written by @bp74

Here is another example to make it clearer:

import 'dart:html';
void main() {
  document.onClick.listen((e) {
    print(window.performance.now());
  });
}

If you continuously click on the document, you get this result:

1032.999999995809
1656.9999999992433
2417.0000000012806
3152.9999999984284
3896.999999997206
4392.999999996391

window.performance.now() should give you milliseconds, but the fraction should give you microseconds.

I'm able to repro this on Chrome Windows, but not Linux.

I assume it's running into this Chrome bug https://code.google.com/p/chromium/issues/detail?id=158234

Resolving as 'As Designed' as I believe the Dart functionality is performing properly, but it's limited by the underlying Chrome implementation.

Added AsDesigned label.

FWIW it seems like windows.performance.now() works better on Mac:

7781.259999999747
60464.874000001146
69156.95100000084
74710.68999999989

This comment was originally written by Misko.H...@gmail.com

pete> Is the request that Stopwatch use window.performance.now in dart2js when possible?

Yes, I think that is the request. We should be using high resolution timer whenever possible.

Stopwatch does use window.performance.now when available (all but Safari).