Browser Diet - Cache Array Length

JavaScript performance comparison

Revision 17 of this test case created by crazy2be

Preparation code

<script>
  var arr = new Array(1000),
      len, i;
  for (i = 0; i < arr.length; i++) {
    arr[i] = i;
  }
</script>

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Testing in unknown unknown
Test Ops/sec
Without cache
for (i = 0; i < arr.length; i++) {
  // do something
}
pending…
With cache
for (i = 0, len = arr.length; i < len; i++) {
  // do something
}
pending…
For each
for (var item in arr) {
  // do something
}
pending…
Array.forEach
function doSomething(element, index, array) {
  // do something
}
arr.forEach(doSomething);
pending…

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