Pro PHP and jQuery by Jason Lengstorf.pdf - Computer Science ...

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CHAPTER 2 ■ COMMON JQUERY ACTIONS AND METHODS
• Access to all attributes of an element, including CSS and styling properties, and
the ability to modify them
• Animation and other effects
• Simple AJAX controls
■ Note The preceding list is only a partial list of jQuery’s features and capabilities. As you continue on through the
projects in this book, other helpful features will be explored. As always, for a complete reference, visit the
documentation at http://api.jquery.com.
Traversing DOM Elements
Traversal in jQuery is the act of moving from one DOM element to another; traversal is essentially
another form of filtering performed after the initial selection has been made. This is useful because it
allows developers to complete an action and then move to another part of the DOM without needing to
perform another search by selector.
It also aids developers in affecting the elements immediately surrounding an element that is being
manipulated or otherwise utilized by a script. This can range from adding a class to parent elements to
indicate activity to disabling all inactive form elements to any number of other useful tasks.
■ Note You will be using the same HTML test file from Chapter 1 for the examples in this chapter as well. If you're
using XAMPP to test locally, point your browser to http://localhost/testing/ to load this file. Make sure the
Firebug console is open and active (see Chapter 1 for a refresher on using the Firebug console).
.eq()
If a set of elements needs to be narrowed down to just one element identified by its index, then you’re
able to use the .eq() method. This method accepts one argument: an index for the desired element. For
.eq(), indices start at 0.
$("p").eq(1);
When executed in the Firebug console, the following returns:
>>> $("p").eq(1);
[ p.foo ]
Additionally, a negative number can be supplied to .eq() to count backward from the end of the
selection set (e.g., passing -2 will return the second-to-last element from the set).