CHAPTER 19
jQuery
jQuery is a popular library for manipulating the DOM and executing Ajax requests.
There’s nothing you can do with jQuery that you can’t do with the DOM API (jQuery
is, after all, built on the DOM API itself), but it offers three main advantages:
• jQuery protects you from idiosyncrasies in the way different browsers implement
the DOM API (especially older browsers).
• jQuery provides a simpler Ajax API (which is welcome because Ajax is used
heavily in today’s websites).
• jQuery provides many powerful and compact enhancements on the built-in
DOM API.
There is a growing community of web developers who feel that jQuery is no longer
necessary with the improvements in the DOM API and browser quality. This com‐
munity touts the performance and purity of “vanilla JavaScript.” It’s true that the first
point (browser idiosyncrasies) is becoming less true over time, but it has not vanished
altogether. I feel that jQuery remains relevant, and provides many features that would
be extremely time-consuming to reimplement in the DOM API. Whether or not you
choose to use jQuery, its ubiquity makes it hard to avoid entirely, and the wise web
developer will know the basics.
The Almighty Dollar (Sign)
jQuery was one of the first libraries to take advantage of JavaScript’s inclusion of the
dollar sign as an identifier. Perhaps it was hubris when the decision was first made,
but given jQuery’s ubiquity today, the decision seems prescient. When you include
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