Using getElementsByClassName

getElementsByClassName, part of the YUI Dom Collection, makes it easy to collect elements that have a given className applied.

To illustrate the use of getElementsByClassName, we'll create a number of <div>s with various combinations of classNames applied. When the document is clicked, we will collect all of the elements that have the className bar.

Add with some markup for the demo elements, including a button to trigger the demo:

Now we will define the function that collects the elements with the className of bar present. The first argument of the getElementsByClassName method is the className we are searching for. The second argument is an optional tagName, which will make the search much quicker. The third argument is an optional ID of an HTMLElement, or an actual HTMLElement object to use as the root node to start from.

To trigger the demo, we will use the YUI Event Utility's on method to listen for clicks on the button.

This is a simple example of how to use the YAHOO.util.Dom.getElementsByClassName method. Keep in mind that the optional arguments should be used whenever possible to maximize the performance of the search.