caching length

JavaScript performance comparison

Revision 23 of this test case created by Wes Jones

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = Math.random();
    }
};
</script>

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
cached
for (var i = 0, len = arr.length; i < len; i++) {
  arr[i] *= 2;
}
pending…
not cached
for (var i = 0; i < arr.length; i++) {
  arr[i] *= 2;
}
pending…
u wot m8
var len = 2;
len *= arr.length;
len -= len / 2;
for (var i = 0; i < len; i++) {
  arr[i] *= 2;
}
pending…
while loop
var len = arr.length;
while (len--) {
  arr[len] *= 2;
}
pending…
do-while loop
var len = arr.length;
do {
  arr[len] *= 2;
} while (len--);
pending…
Prefix Increment
for (var i = 0; i < arr.length; ++i) {
  arr[i] *= 2;
}
pending…
Prefix + Cached
for (var i = 0, len = arr.length; i < len; ++i) {
  arr[i] *= 2;
}
pending…
Array map
arr.map(function(el) {
  return el * 2;
});
pending…
No Length
var i = 0;
while(arr[i] !== undefined) {
  arr[i] *= 2;
  i += 1;
}
pending…

Compare results of other browsers

Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

0 comments

Add a comment