Benchmark: Loop Optimization

Loop Optimization (version: 0)

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]); }
forEach
arr.forEach(function(arrI){ someFn(arrI); });

Rendered benchmark preparation results:

Previous results

Test case name	Result
For loop, basic
While loop, basic
For loop, cached (inside for statement)
For loop, cached (outside for statement)
For loop, i-- (caching inside for loop)
For loop, i-- (caching outside for loop)
While loop, cached
While loop, i--
forEach

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Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36

Browser/OS: Chrome 85 on Windows

Test name	Executions per second
For loop, basic	4090.4 Ops/sec
While loop, basic	4199.2 Ops/sec
For loop, cached (inside for statement)	6324.0 Ops/sec
For loop, cached (outside for statement)	6270.9 Ops/sec
For loop, i-- (caching inside for loop)	6440.5 Ops/sec
For loop, i-- (caching outside for loop)	6575.9 Ops/sec
While loop, cached	6004.6 Ops/sec
While loop, i--	6242.0 Ops/sec
forEach	12254.4 Ops/sec