core-js/es6/promise from 2.5.7 causes a slowdown on some array operations.

[vlajos]

The same thing happens as described here: #377
when I used the promise module like this:

import 'core-js/es6/promise';

I used this timer script to "detect" the issue:

var arr = [];
for (var i=0; i<3200000; i++) {
    arr.push(Math.random())
}
var startTime = performance.now();

x = new Float32Array(arr);

document.write('Time spent: ' + (performance.now() - startTime) + ' ms');

The time needed to run the loop is around 100x bigger when the promise is imported.

(If you think it helps I am happy to create similar more detailed test scripts like in the other issue.)

[zloirock]

What about core-js@3? I have no ideas how it can touch typed arrays. I'll test it later.

[vlajos]

@zloirock With 3.0.0-beta.3 our app seems to be quick.

[zloirock]

I don't wanna rewrite all possible problem cases in legacy core-js@2 branch if it works in core-js@3. Feel free to add a PR to v2 branch if performance of core-js@2 is something critical for you.