Get All Elements in an HTML document with a specific CSS Class

Question

What\'s the best way to get an array of all elements in an html document with a specific CSS class using javascript?

No javascript frameworks like jQuery allowed her

Answer 1

The below answer is now pushing four years old, so it's worth noting that native browser support for getElementsByClassName() has gotten a lot better. But if you must support older browsers, then...

Use one that's already been written. Most major JS libraries include one in some form or another, but if you aren't using one of them then i can recommend Robert Nyman's excellent implementation:

http://code.google.com/p/getelementsbyclassname/
http://www.robertnyman.com/2008/05/27/the-ultimate-getelementsbyclassname-anno-2008/

There are just too many ways to make this (conceptually-simple) routine slow and buggy to justify writing your own implementation at this point.