Thanks to a suggestion from Johnathan Snook, here is a summary of the results of the benchmarking I did on my favorite loop:
Method 1 uses for (var i=0; i<test.length; i++)
Method 2 uses for (var i=0, l=test.length; i<l; i++)
Method 3 uses for (var i=0, o; o=test[i]; i++)
| Method | Firefox 1.5 PC | IE 6.0 PC | Safari |
| 1 | 0ms | 16ms | 11ms |
| 2 | 0ms | 0ms | 12ms |
| 3 | 0ms | 0ms | 10ms |
| Method | Firefox 1.5 PC | IE 6.0 PC | Safari |
| 1 | 31ms | 32ms | 125ms |
| 2 | 16ms | 15ms | 117ms |
| 3 | 16ms | 16ms | 96ms |
| Method | Firefox 1.5 PC | IE 6.0 PC | Safari |
| 1 | 297ms | 266ms | 1937ms |
| 2 | 296ms | 250ms | 1924ms |
| 3 | 250ms | 203ms | 1878ms |
Here’s a link to the script I used for benchmarking.
{ 2 comments… read them below or add one }
Just adding the results of the test for Opera 9.0 weekly build 8367.
1,000 Iterations
———————
1. 0ms
2. 0ms
3. 0ms
10,000 Iterations
———————
1. 40ms
2. 30ms
3. 30ms
100,000 Iterations
———————
1. 340ms
2. 341ms
3. 280ms
Doing the test multiple times resulted in different results, but method 3 was consistently the fastest.
Unfortunately the loops as shown are not equilivant folks.
Try running the 3rd one with 0, “”, false, or null as any one of the array values instead of the “1 to iterations” integers within the test array, and you’ll find that your looping will not loop around all of the elements in the array, but rather stop at the first ocurance of 0, “”, or null.
I suppose that if you can guarantee that you’ll only ever have non-0, non-”", non-false, non-null data in your array you might be able to get away with using this type of construct, but even then, you be giving up guaranteed working for just a few milliseconds. And even at 100,000 iterations (when’s the last time anyone really needed an array that large?), in the worst performing browser, the difference is only 46 milliseconds, which isn’t going to be noticable.