In ts.performance.now, bind window.performance.now

[sandersn]

Fixes #9954

Using an arrow function. Previously, it was set directly to window.performance.now, which fails when used in Chrome.

[sandersn]

Incidentally, I ripped off Date.now in both Chrome and Node and it works fine that way.

[weswigham]

👍 It's always a little disappointing how inconsistent the web is with what you can rip off its hosting object and what you cannot.

[sandersn]

And neither Date nor performance document it, in the documentation I found at least.

[weswigham]

@sandersn That was why I thought it was okay to rip both off. 😞

[sandersn]

One of the Mac builds timed out. I think it's OK to merge anyway.

[weswigham]

@sandersn This has been happening every few builds - I actually restarted a build last night that had been running for over an hour (I just assumed travis had hung). I don't know if it's a random pathological perf problem in TS that's only exposed on mac, or an issue with the travis infrastructure.

[mihailik]

FYI: compared () => performance.now() with performance.now.bind(performance), the arrow function is faster on my Chrome, faster in FireFox — but slower on IE11.

Don't have an Edge to try.

Here's the code below to run in DevTools console:

var runAndAgain = function() {
  setTimeout(function() {
    runMillion();
    runAndAgain();
  }, 1);
};
runAndAgain();

function runMillion() {

  var now_arrow = function() { return performance.now(); };
  var now_bind = performance.now.bind(performance);

  var start = new Date(), tmp=0;
  for (var i = 0; i < 1000000; i++) { tmp = now_arrow(); }
  var arrow_time = new Date() - start;

  var start = new Date(), tmp=0;
  for (var i = 0; i < 1000000; i++) { tmp = now_bind(); }
  var bind_time = new Date() - start;

  console.log('arrow '+arrow_time+'\tbind '+bind_time+'\t ratio '+(((10000*arrow_time/bind_time)|0)/100)+'%');
}

[sandersn]

Does anybody use IE11 to debug TypeScript? Faster in Chrome is better in my book.

[weswigham]

AFAIK, most of the team doesn't use IE, so the faster in chrome/FF option does seem better.

[mihailik]

I totally agree, Chrome is a better target -- and the difference is small enough anyway. Only wanted to give more context 👍