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YUI Library Examples: Dom Collection: Using getElementsByClassName

Dom Collection: Using getElementsByClassName

Clicking the document will use Dom's getElementsByClassName method to collect all of the elements with the class bar applied.

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div class="bar"
div class="bar-baz"
div class="bar "
div class=" bar "
div class=" bar baz"
div class=" bar2 baz"
div class="foo"
div class="foo" id="bar"
div class="foo bar baz"

p class="bar"

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:

1<div class="bar">div class="bar"</div> 
2<div class="bar-baz">div class="bar-baz"</div> 
3<div class="bar ">div class="bar "</div> 
4<div class=" bar ">div class=" bar "</div> 
5<div class="bar baz">div class=" bar baz"</div> 
6<div class="bar2 baz">div class=" bar2 baz"</div> 
7<div class="foo">div class="foo"</div> 
8<div class="foo" id="bar">div class="foo" id="bar"</div> 
9<div class="foo bar baz">div class="foo bar baz"</div> 
10<p class="bar">p class="bar"</p> 
11<button id="demo-run">run</button> 
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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.

1<script type="text/javascript"> 
2    var getByClass = function() { 
3        alert('found: ' + YAHOO.util.Dom.getElementsByClassName('bar', 'div').length + ' elements'); 
4    }; 
5</script> 
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To trigger the demo, we will use the YUI Event Utility's on method to listen for clicks on the button.

1<script type="text/javascript"> 
2    YAHOO.util.Event.on('demo-run', 'click', getByClass); 
3</script> 
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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.

Configuration for This Example

You can load the necessary JavaScript and CSS for this example from Yahoo's servers. Click here to load the YUI Dependency Configurator with all of this example's dependencies preconfigured.

YUI Logger Output:

Logger Console

INFO 70ms (+3) 8:28:21 PM:
Dom
isAncestor([object HTMLHtmlElement],[object HTMLSpanElement] returning true
INFO 67ms (+28) 8:28:21 PM:
Dom
getElementsBy returning 
INFO 39ms (+0) 8:28:21 PM:
Dom
generateId generating yui-log-filter-Dom010
WARN 39ms (+0) 8:28:21 PM:
Dom
batch called with invalid arguments
INFO 39ms (+0) 8:28:21 PM:
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INFO 38ms (+0) 8:28:21 PM:
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generateId generating yui-log-filter-Get08
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INFO 38ms (+0) 8:28:21 PM:
Dom
generateId generating yui-log-filter-example07
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INFO 38ms (+0) 8:28:21 PM:
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generateId generating yui-log-filter-global06
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INFO 38ms (+0) 8:28:21 PM:
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generateId generating yui-log-filter-window05
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INFO 38ms (+0) 8:28:21 PM:
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generateId generating yui-log-filter-time04
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INFO 38ms (+0) 8:28:21 PM:
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generateId generating yui-log-filter-error03
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batch called with invalid arguments
INFO 38ms (+0) 8:28:21 PM:
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generateId generating yui-log-filter-warn02
WARN 38ms (+0) 8:28:21 PM:
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INFO 38ms (+0) 8:28:21 PM:
Dom
generateId generating yui-log-filter-info01
WARN 38ms (+1) 8:28:21 PM:
Dom
batch called with invalid arguments
INFO 37ms (+1) 8:28:21 PM:
Dom
generateId generating yui-log-hd00
INFO 36ms (+9) 8:28:21 PM:
LogReader  instance0
LogReader initialized
INFO 27ms (+1) 8:28:21 PM:
Get
Appending node: ../../../2.x/build/event-mouseenter/event-mouseenter-min.js
INFO 26ms (+0) 8:28:21 PM:
Get
attempting to load ../../../2.x/build/event-mouseenter/event-mouseenter-min.js
INFO 26ms (+24) 8:28:21 PM:
Get
_next: q0, loaded: undefined
INFO 2ms (+2) 8:28:21 PM:
example
The example has finished loading; as you interact with it, you'll see log messages appearing here.
INFO 0ms (+0) 8:28:21 PM:
global
Logger initialized

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