Benchmark: Map vs For Loop - MeasureThat.net

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; }
++for loop
var b = new Array(a.length); for (var i = 0; i < a.length; ++i) { b[i] = a[i] * 2; }
--for loop
var b = new Array(a.length); for (var i = a.length; i >= 0; --i) { b[i] = a[i] * 2; }

Rendered benchmark preparation results:

Previous results

Test case name	Result
Map
For Loop
foreach
pre-allocated for loop
pre-allocated unrolled for loop
++for loop
--for loop

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Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:92.0) Gecko/20100101 Firefox/92.0

Browser/OS: Firefox 92 on Mac OS X 10.15

Test name	Executions per second
Map	67.0 Ops/sec
For Loop	75.1 Ops/sec
foreach	160.8 Ops/sec
pre-allocated for loop	77.7 Ops/sec
pre-allocated unrolled for loop	76.7 Ops/sec
++for loop	75.4 Ops/sec
--for loop	8.3 Ops/sec

Map vs For Loop (version: 0)