Learning jQuery

If you haven’t poked around under the hood of jQuery, you might not be aware that when you pass the jQuery function an expression or DOM element it places these elements (or, possibly a single element) into an object, and then this object is returned so that it can be chained. Without getting into the details of chaining, the fundamental concept to remember is this:

Most jQuery methods return the jQuery object itself, which allows methods to be chained.

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A common feature I’ve seen on “web 2.0” sites and wikis is the “external link” icon: . While I’m not crazy about the idea of sticking these little images all over the HTML, they’re a great candidate for using progressive enhancement. In our case, we can use jQuery to add the images pretty easily.

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After many months of stellar work, the jQuery UI team has released version 1.5 of their flagship suite of user-interface widgets, components, and effects. This release was focused on bringing you a standardized development API across all of the components, allowing for a more seamless experience when working with the jQuery UI library.

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In my last article, I described the common problem of events seemingly ceasing to work for new elements added to a document, whether by some form of ajax or by DOM modification. We examined one way to overcome the problem: Event Delegation. With event delegation, we bind the event handler to a containing element that remains in the DOM and then check for the target of the event.

Cloning Nodes

This time, we’ll take a look at re-binding event handlers. But before we do, I should mention that, as of jQuery version 1.2, event handlers can be cloned along with elements. Consider this unordered list:

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Recently I have been getting a real buzz out of developing with jQuery. I’ve been using the library since 2006, releasing sporadic bits of code. In April of this year, I released the third revision of my most complex plugin, jMaps, and updated several other plugins, which are available in my mercurial repository.

This was also the same month I discovered a new plugin which has dramatically changed how I develop applications with jQuery. The plugin in question is Dan Webb’s Low Pro for jQuery, a port of the plugin of the same name for Prototype.

What is Low Pro?

So what is Low Pro? It’s a plugin that provides a way of making more object-oriented JavaScript through event delegation. jQuery’s plugin architecture provides a really simple way of extending the core functionality, but there is no easy way of making macros of code that do several types of events on one element. Until now!

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CSS and JavaScript are different in many ways, almost all of which are too obvious to mention. However, one difference between the two bears explanation, because it is often the cause of confusion and consternation, especially among those who are making the transition from CSS guru to jQuery novice. In fact, it was one of the first things I asked about on the jQuery mailing list back in 2006. Since then, I’ve seen at least one question on the subject every week, and sometimes as many as one per day—despite an FAQ page and these three plugins to help users deal with it.

How CSS and JavaScript Are Different

So, what’s this important difference?

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