Run results for: Loop Optimization

Run details:

User agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0

Browser: Firefox 57

Operating system: Windows 7

Device Platform: Other

Date tested: 2025 years ago

Test name	Executions per second
For loop, basic	2864.8 Ops/sec
While loop, basic	2972.4 Ops/sec
For loop, cached (inside for statement)	3549.1 Ops/sec
For loop, cached (outside for statement)	3606.1 Ops/sec
For loop, i-- (caching inside for loop)	3610.7 Ops/sec
For loop, i-- (caching outside for loop)	3697.6 Ops/sec
While loop, cached	3627.7 Ops/sec
While loop, i--	3689.3 Ops/sec
forEach	4149.7 Ops/sec

Script Preparation code:

  var arr = [];
  for (var i = 0; i < 10000; i++) {
    arr.push(i);
  }

var sum = 0;

Tests:

For loop, basic
for (var i = 0; i < arr.length; i++) { sum += arr[i]; }
While loop, basic
var i = 0; while (i < arr.length) { sum += arr[i]; i++; }
For loop, cached (inside for statement)
for (var i = 0, len = arr.length; i < len; i++) { sum += arr[i]; }
For loop, cached (outside for statement)
var len = arr.length; for (var i = 0; i < len; i++) { sum += arr[i]; }
For loop, i-- (caching inside for loop)
for (var i = arr.length; i > 0; i--) { sum += arr[i]; }
For loop, i-- (caching outside for loop)
var i = arr.length; for (; i--;) { sum += arr[i]; }
While loop, cached
var len = arr.length; var i = 0; while(i < len){ sum += arr[i]; i++; }
While loop, i--
var i = arr.length; while(i--){ sum += arr[i]; }
forEach
arr.forEach(function(val){ sum += val; });