Info

Storing the length property of an array that will be iterated through with a for loop into a variable is an old school performance optimization for JavaScript. Browsers have since evolved to better handle these sorts of minor optimizations. Interested in seeing whether this optimization is still beneficial in today's browsers.

Preparation code

 
<script>
  Benchmark.prototype.setup = function() {
    var i, l, x, arr = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"];
  };
</script>

Test runner

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

Java applet disabled.

for (i = 0, l = arr.length; i < l; i++) { x = arr[i]; }

for (i = 0; i < arr.length; i++) { x = arr[i]; }

You can edit these tests or add even more tests to this page by appending /edit to the URL.

Compare results of other browsers

0 comments