jQuery Intro

jQuery

Jason Noblehttp://jasonnoble.org

Code Download: http://jasonnoble.org/jquery/jquery.zip

History

• John Resig hints of a JavaScript library to use CSS selectors with a more succint syntax than existing libraries (2005)

• First release January 2006

Benefits

• Easy to play with the DOM• Add JS effects• AJAX• Cross-browser Compatibility

– jQuery handles browser caveats for you• CSS3 Selectors• Helpful Utilities

Benefits (cont.)

• jQuery UI– Useful effects– Advanced UI widgets– UI Themes

• Plugins– jQuery is easily extensible

• Widespread adoption

Firefox/Firebug Combo

• Firefox• Firebug plugin

Let’s get Started

• curl -o jquery-1.4.4.min.js http://code.jquery.com/jquery-1.4.4.min.js

• vi hello.html

jQuery Function

• Adding jQuery to a HTML page gives you access to the jQuery function– jQuery– jQuery(alert(‘Hello’))

• jQuery function is aliased as $– $– $(alert(‘Hello’))

Document Object Model (DOM)

• Not specific to jQuery• Standard way of representing objects in

HTML that all browsers follow• Hierarchal representation of your HTML• Parent and children elements• Each element can have an id and/or

one or more class attributes

DOM (Cont.)

Elements id

• Uniquely identifies the element

<div id=“footer”>Thanks for visiting</div>

• That div’s id is “footer”. Should only be one “footer” id.

Elements class

• Multiple page elements can have the same type of class

<p class=“warning”>Sorry….</p><span class=“warning error”>Please try again</span>

• Classifies elements as a “warning”• Multiple classes on an element are seperated

by spaces

CSS Selectors

• # selects an element via id– div#heading

• <div id=“heading”>

• . selects an element via class– div.heading

• <div class=“heading”>

• Bare words selects HTML tags– span

• <span>

Update our HTML

jQuery Statements

selector action parameters jQuery(‘p’) .css (‘color’, ‘blue’); $(‘p’) .css (‘color’, ‘blue’);

$(‘p’) .css (‘font-size’, ‘35px’);

jQuery Statements

• $('#one').css('color', 'green');

• $('.not_first').css('font-size', '22pt');

• $('p.first').html('This is better');

Document Ready Event

• When our document is ready, run our function

<script> $(document).ready(function() { alert(‘Welcome to my page!’); });</script>• This is a fairly common code snippet

Play with tables

jQuery filters

• Removes certain elements– $(‘table tr:even’) # => 0, 2, 4, 6…– $(‘table tr:odd’) # => 1, 3, 5, 7…– $(‘table tr:first’) # => 0– $(‘table tr:last’) # => Last row– $(‘table tr:eq(3)’) # => Third row

Play with tables (cont.)$('table tr:even').css('background-color', 'lightgrey')

$('table tr:first').css('font-size', '64pt')

$('table tr td').filter(function(index) { return index % 3 == 2;}).css('color', 'red')

Many more selectors: http://api.jquery.com/category/selectors/

Playing with Ajax

• Asynchronous JavaScript and XML• Allows you to update elements on your

page without refreshing the entire page• Google suggest was one of the first

sites to use it (2005)

load.html

Ajax Content

ajaxStart / ajaxStop

• $(document).ajaxStart(…)– Called when an ajax request is started

• $(document).ajaxStop(…)– Called when an ajax request is complete

$(selector).click(…)

• Executes code when a given div/button/etc is clicked

Username Validation

• Uses a jQuery plugin (jquery.validate)• http://bassistance.de/jquery-plugins/jque

ry-plugin-validation/