Array direct assignment vs push

JavaScript performance comparison

Revision 64 of this test case created

Info

Math.random() is pretty heavy operation to have it in test case. Also removed preparation code from test cases. For loop length should be much longer to test more of array manipulation then loop preparation.

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var values = [],
      count = 100000;
   
    for (var i = 0; i < count; i++) {
      values[i] = i;
    }
};
</script>

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Testing in unknown unknown
Test Ops/sec
Direct assignment
var array = Array(count);
for (var i = 0; i < count; i++) {
  array[i] = values[i];
}
pending…
Push
var array = [];
for (var i = 0; i < count; i++) {
  array.push(values[i]);
}
pending…
Accessing length property
var array = [];
for (var i = 0; i < count; i++) {
  array[array.length] = values[i];
}
pending…
Cached length
var arrayLength = 0;
var array = [];
for (var i = 0; i < count; i++) {
  array[arrayLength++] = values[i];
}
pending…

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Revisions

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