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]); }

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--

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Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36

Browser/OS: Chrome 76 on Windows

Test name	Executions per second
For loop, basic	3264.0 Ops/sec
While loop, basic	3147.3 Ops/sec
For loop, cached (inside for statement)	5092.2 Ops/sec
For loop, cached (outside for statement)	5373.7 Ops/sec
For loop, i-- (caching inside for loop)	5192.6 Ops/sec
For loop, i-- (caching outside for loop)	5287.7 Ops/sec
While loop, cached	5155.0 Ops/sec
While loop, i--	5408.2 Ops/sec