Learning jQuery

In the beginning (well, beginning with jQuery 1.2.3 in early 2008) there was the jQuery.data() API. It offers a way to associate JavaScript data — strings, numbers, or any object — with a DOM element. As long as you manipulate the DOM element with jQuery, the library ensures that when the DOM element goes away, the associated data goes away as well. This is especially important for older versions of IE that tend to leak memory when JavaScript data is mixed with DOM data.

Most jQuery code sets data values using the higher-level .data() API; for example, $("div").data("imaDiv", true) sets a boolean value on every div in the document. This API, in turn, calls down to jQuery.data() with each element to set the value. For completeness, there are also jQuery.removeData() and .removeData() to remove data elements, and jQuery.hasData() to determine if any data is currently set for an element.

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Editor’s Note: When I started this blog nearly three years ago, one of the first things I did was write a series on showing and hiding elements on a page. The posts were very basic, as was my knowledge at the time. At best, they demonstrated an incomplete answer to the question of how to selectively reveal content based on user interaction. At worst, they encouraged a solution without any regard to accessibility. That’s why I was thrilled when I saw an article on the Filament Group blog describing their accessible collapsible content widget. They’ve graciously accepted my request to re-post that article here, so without any further ado, here it is…

Collapsible content areas are frequently presented in web sites and applications as a way to let users to control how content is shown or hidden on the page. Also called collapsibles, spin-downs, toggle panels, twisties, and content disclosures, they’re ideal for selectively displaying optional information — like instructional text or additional details, for example — so users can focus on the task at hand and view this content only as needed.

The collapsible content area widget is fairly simple — a couple of HTML elements controlled with minimal CSS and JavaScript — but when we were researching our book, Designing with Progressive Enhancement, we discovered that many common approaches to creating collapsible content fail to incorporate accessibility features. Happily, there is a way to build collapsible content with progressive enhancement so it delivers an optimal accessible experience for sighted and screen reader users alike.

The code example described in this article is one of the 12 fully-accessible, project-ready, progressive enhancement-driven widgets that accompanies our new book, Designing with Progressive Enhancement.

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When working with an Ajax-enhanced website, it’s generally a good idea to provide a regular request fallback for any core functionality of the site. When you work to ensure that a fallback is in place, you will be faced with determining when a particular request is an Ajax request or just a normal page request. In most situations, it’s considered a best practice to build your site without Ajax first, adding the Ajax functionality afterward so the fallbacks are in place from the beginning.

Fortunately, jQuery makes it super easy to differentiate the Ajax requests from normal page views.

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As some of you have heard, there have been two new methods added in jQuery 1.4.2, .delegate() and .undelegate(). These methods achieve the same thing as the .live() and .die() methods, they just use a different syntax. For those new to .live(), it’s a method in jQuery that allows you to attach events to elements that appear in the document as well as elements that will appear in the future. An example would be if you attached a click event via .live():

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Event delegation, as described in the first article of this series, is a way to take advantage
of event bubbling to avoid binding an event listener more than once. jQuery 1.3 and the upcoming jQuery 1.4
have many features that make using event delegation in your web pages easier.
The aim of this tutorial is to help you understand how these new features work. Read the rest of this entry »

In this tutorial I’ll show you how to create a navigation menu that slides horizontally. It begins with a set of “tabs” on the right side of a containing element. When clicked, a tab slides to the left to reveal a group of links. Click the tab again, and it slides back. While I’ve never had a need to build one of these for any of my own projects, quite a few people have asked if I would demonstrate how it might be done, so here goes. Read the rest of this entry »