for loop length caching

JavaScript performance comparison

Revision 4 of this test case created

Preparation code

  var arr = [],
      counter = 0;
  while (arr.length < 10000000) {
   arr[arr.length] = Math.floor(Math.random() * 16383);

Test runner

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

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
No caching
for (var i = 0; i < arr.length; i++) {
 counter += arr[i];
Length property caching
for (var i = 0, length = arr.length; i < length; i++) {
 counter += arr[i];

Compare results of other browsers


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:


Comment form temporarily disabled.

Add a comment