Run results for: Loop Optimization

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0

Browser: Firefox 62

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 5 years ago

Test name	Executions per second
For loop, basic	106104.1 Ops/sec
While loop, basic	105878.0 Ops/sec
For loop, cached (inside for statement)	148417.3 Ops/sec
For loop, cached (outside for statement)	145266.5 Ops/sec
For loop, i-- (caching inside for loop)	146427.2 Ops/sec
For loop, i-- (caching outside for loop)	149411.6 Ops/sec
While loop, cached	147504.7 Ops/sec
While loop, i--	151303.3 Ops/sec

Script Preparation code:

  var arr = [];
  for (var i = 0; i < 1000; i++) {
    arr[i] = i;
  }

  function someFn(ix) {
    return ix * 5 + 1 / 3 * 8;
  }

Tests:

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