Run results for: Map vs For Loop

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:51.0) Gecko/20100101 Firefox/51.0

Browser: Firefox 51

Operating system: Windows

Device Platform: Other

Date tested: 7 years ago

Test name	Executions per second
Map	123.0 Ops/sec
For Loop	89.3 Ops/sec
foreach	2106.8 Ops/sec
pre-allocated for loop	82.9 Ops/sec
pre-allocated unrolled for loop	103.2 Ops/sec

Script Preparation code:

var a = [];
for (var i = 0; i < 1e6; i++) {
  a[i] = Math.random();
}

Tests:

Map
var b = a.map(n => n * 2);
For Loop
var b = []; for (var i = 0; i < a.length; i++) { b[i] = a[i] * 2; }
foreach
var b = a.forEach(n => n * 2);
pre-allocated for loop
var b = new Array(a.length); for (var i = 0; i < a.length; i++) { b[i] = a[i] * 2; }
pre-allocated unrolled for loop
var b = new Array(a.length); for (var i = 0; i < a.length/4; i++) { b[i*4] = a[i*4] * 2; b[i*4+1] = a[i*4+1] * 2; b[i*4+2] = a[i*4+2] * 2; b[i*4+3] = a[i*4+3] * 2; }