jQuery in 15 minutes
Torchbox, 7th August 2007

What makes jQuery
interesting?
• Built around CSS selectors
• Well behaved
• Doesn’t hijack your global namespace
• Plays well with other libraries
• API designed with conciseness and
convenience as the driving factors

The jQuery() function
jQuery('div#intro h2')
jQuery('div.section > p')
jQuery('input:radio')
$('div#intro h2')

jQuery collections
• $('div.section') returns a jQuery collection
• You can call methods on it:
$('div.section').size() = no. of matched elements
$('div.section').each(function(div) {
// Manipulate the div
}

Manipulating collections
• Most jQuery methods operate on all of the
matched elements in the collection
$('div.section').addClass('highlighted')
$('img.photo').attr('src', '/default.png');
$('a.foo').html('<em>Click me now!</em>');
$('p:odd').css('background-color', '#ccc');

Grabbing values
• Some methods return results from the first
matched element
var height = $('div#intro').height();
var src = $('img.photo').attr('src');
var lastP = $('p:last').html()

Traversing the DOM
• jQuery provides enhanced methods for
traversing the DOM
$('div.section').next()
$('div.section').prev()
$('div.section').prev('a')
$('div.section').parent()
$('div.section').parents()

Handling events
• jQuery provides methods for assigning event
handlers to elements in a cross-browser way
$('a').click(function(ev) {
$(this).css({backgroundColor: 'orange'});
ev.preventDefault();
});

Going unobtrusive
$(document).ready(function() {
alert('The DOM is ready!');
});
$(function() { alert('This is a shortcut') });

Chaining
• Most jQuery methods return another
jQuery object - often one representing the
same collection. This means you can chain
methods together:
$('div.section').hide().addClass('gone');

Crazy chaining
$('form#login')
// hide all the labels inside the form with the 'optional' class
.find('label.optional').hide().end()
// add a red border to any password fields in the form
.find('input:password').css('border', '1px solid red').end()
// add a submit handler to the form
.submit(function(){
return confirm('Are you sure you want to submit?');
});
From http://www.ibm.com/developerworks/library/x-ajaxjquery.html

Ajax
• jQuery has excellent support for Ajax
$('div#intro').load('/some/file.html');
• More advanced methods include:
$.get(url, params, callback)
$.post(url, params, callback)
$.getJSON(url, params, callback)
$.getScript(url, callback)

Plugins
• jQuery is extensible through plugins, which
can add new methods to the jQuery object
• Form: better form manipulation
• Dimensions: lots of browser measurements
• Interface: fancy effects, accordions
• UI: drag and drop, and more

Further reading
• http://jquery.com/ - official site
• http://visualjquery.com/ - useful API reference