Caching Array Length

JavaScript performance comparison

Revision 42 of this test case created

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var theArray = [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1];
    var copyOfTheArray = [];
};
</script>

Test runner

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Testing in unknown unknown
Test Ops/sec
With caching
var len = theArray.length;
for (var i = 0; i < len; i++) {
  copyOfTheArray[i] = theArray[i];
}
pending…
Without caching
for (var i = 0; i < theArray.length; i++) {
  copyOfTheArray[i] = theArray[i];
}
pending…
With caching Part 2
var i = 0;
for (var x in theArray) {
  copyOfTheArray.push(x);
  i++;
}
pending…
while
var len = theArray.length;
while (len--) {
   copyOfTheArray[len] = theArray[len];
}
pending…

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