push allocated vs dynamic

JavaScript performance comparison

Revision 7 of this test case created

Info

is it usefull to pre-allocate the array by setting the last value first when assigning some values ?

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var n = 100000;
    var myArray = [];
    var myArray2 = new Array(n);
    var myArray3 = new Array();
};
</script>

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Testing in unknown unknown
Test Ops/sec
push
for (var i = 0; i < n; i++) {
  myArray.push(i)
}
pending…
reverse writing
  var i = n;
  while (i--) {
    myArray[i] = i
  }
pending…
reverse writing, array allocated with Array constructor
  var i = n;

  while (i--) {
    myArray2[i] = i
  }
pending…
direct set
for (var i = 0; i < n; i++) {
  myArray[i] = i;
}
pending…
preallocate direct set
  for (var i=0;i<n; ++i) {
    myArray2[i] = i
  }
pending…
preallocate push
  for (var i=0;i<n; ++i) {
    myArray3.push(i);
  }
pending…

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