Fastest array loops in Javascript

JavaScript performance comparison

Revision 86 of this test case created by Visha

Preparation code

<script>
  // Populate the base array
  var arr = [];
  for( var i = 0; i < 1000; i++ ) {
    arr[i] = 'value' + i;
  }

  function someFn (ix) {
      return ix * 5 + 1 / 3 * 8;
  }
</script>
    

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
For loop, basic
for (var i = 0; i < arr.length; i++) {
  someFn(i);
}
pending…
While loop, basic
var i = 0;
while (i < arr.length) {
  someFn(i);
  i++;
}
pending…
For loop, cached
for (var i = 0, len = arr.length; i < len; i++) {
  someFn(i);
}
pending…
For loop, i--
for (var i = arr.length - 1; i >= 0; i--) {
  someFn(i);
}
pending…
Do-while loop, i--
var i = arr.length - 1;
do {
  someFn(i);
}
while (i--);
pending…
Do-while loop, --i
var i = arr.length;
if (i > 0) {
  do {
    someFn(i);
  }
  while (--i);
}
pending…
Magic For Loop
for (var i = arr.length; i--;) {
  someFn(i);
}
pending…

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Revisions

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