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# YUI Library Examples: Selector Utility: Using filter

# Selector Utility: Using filter

Clicking the button will alert the number of items with the class of "selected" applied.

View example in new window.

- lorem
- ipsum
- dolor
- sit

- lorem
- ipsum
- dolor
- sit

- lorem
- ipsum
- dolor
- sit

1. lorem
2. ipsum
3. dolor
4. sit

## Using filter

The filter method, part of the YUI Selector Utility, makes it easy to filter a set of nodes based on a CSS3 Selector.

To illustrate the use of filter, we'll create a few HTML lists. When the button is clicked, we filter the collection of `LI`elements, so that only those that have the class `selected` applied are left in the array.

Add some markup for the lists and a button to trigger the demo:

<ul> <li class="selected">lorem</li> <li>ipsum</li> <li>dolor</li> <li>sit</li> </ul> <ul> <li>lorem</li> <li class="selected">ipsum</li> <li>dolor</li> <li>sit</li> </ul> <ul> <li>lorem</li> <li>ipsum</li> <li>dolor</li> <li class="selected">sit</li> </ul> <ol> <li>lorem</li> <li>ipsum</li> <li>dolor</li> <li class="selected">sit</li> </ol> <button id="demo-run">run</button>

Now we will define the function that filters the nodes when the button is clicked, and assign it as a click handler.

<script type="text/javascript"> var nodes = document.getElementById('selector-demo').getElementsByTagName('li'); var handleClick = function(e) { nodes = YAHOO.util.Selector.filter(nodes, '.selected'); alert(nodes.length); }; YAHOO.util.Event.on('demo-run', 'click', handleClick); </script>

This is a basic example of how to use the `Selector.filter` method.

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### Selector Utility Examples:

### More Selector Utility Resources:

- User's Guide (external)
- API Documentation
- Cheat Sheet PDF (external)

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