Benchmark: Loop Optimization Working

Loop Optimization Working (version: 1)

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 > 0; 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 - 1; while(i > 0){ someFn(arr[i]); i--; }
map
arr.map(i => someFn(i))
forEach
arr.forEach(i => someFn(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--
map
forEach

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Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36

Browser/OS: Chrome 84 on Linux

Test name	Executions per second
For loop, basic	2134.0 Ops/sec
While loop, basic	2198.2 Ops/sec
For loop, cached (inside for statement)	2927.5 Ops/sec
For loop, cached (outside for statement)	3325.2 Ops/sec
For loop, i-- (caching inside for loop)	3298.9 Ops/sec
For loop, i-- (caching outside for loop)	3220.6 Ops/sec
While loop, cached	2067.5 Ops/sec
While loop, i--	2114.1 Ops/sec
map	3484.8 Ops/sec
forEach	3860.6 Ops/sec