Cody Lindley - DOM Enlightenment

Beijing Cambridge Farnham Kln Sebastopol Tokyo

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I make websites. Sometimes I make music. Over the years, Ive noticed an interesting pattern of behavior from some musiciansoften self-taughtwho think of themselves as creative types: they display an aversion to learning any music theory. The logic, they say, is that knowing the theory behind music will somehow constrain their creative abilities. Ive never understood that logic (and I secretly believe that its a retroactive excuse for a lack of discipline). To my mind, I just dont see how any kind of knowledge or enlightenment could be a bad thing.

Alas, I have seen the same kind of logic at work in the world of web design. There are designers who not only dont know how to write markup and CSS, they actively refuse to learn. Again, they cite the fear of somehow being constrained by this knowledge (and again, I believe thats a self-justifying excuse).

In the world of front-end development, that attitude is fortunately far less prevalent. Most web devs understand that theres always more to learn. But even amongst developers who have an encyclopediac knowledge of HTML and CSS, there is often a knowledge gap when it comes to the Document Object Model. Thats understandable. You dont need to understand the inner workings of the DOM if youre using a library like jQuery. The whole point of JavaScript libraries is to abstract away the browsers internal API and provide a different, better API instead.

Nonetheless, I think that many front-end devs have a feeling that they should know whats going on under the hood. Thats the natural reaction of a good geek when presented with a system theyre expected to work with. Now, thanks to DOM Enlightenment , they can scratch that natural itch.

Douglas Crockford gave us a map to understand the inner workings of the JavaScript language in his book JavaScript: The Good Parts . Now Cody Lindley has given us the corresponding map for the Document Object Model. Armed with this map, youll gain the knowledge required to navigate the passageways and tunnels of the DOM.

You might not end up using this knowledge in every project. You might decide to use a library like jQuery instead. But now it will be your decision. Instead of having to use a library because thats all that you know, you can choose if and when to use a library. Thats a very empowering feeling. Thats what knowledge provides. That is true enlightenment.

This book is not an exhaustive reference on DOM scripting or JavaScript. It may, however, be the most exhaustive book written about the HTML DOM without the use of a library/framework. The lack of authorship around this topic is not without good reason. Most technical authors are not willing to wrangle this topic because of the differences that exist among legacy browsers and their implementations of the DOM specifications (or lack thereof).

For the purpose of this book (i.e., grokking the concepts), Im going to sidestep the browser API mess and dying browser discrepancies in an effort to expose the modern DOM. Thats right, Im going to sidestep the ugliness in an effort to focus on the here and now. After all, we have solutions such as jQuery to deal with all that browser ugliness, and you should definitely be leveraging something like jQuery when dealing with deprecated browsers.

While I am not promoting the idea of only going native when it comes to DOM scripting, I did write this book in part so that developers may realize that DOM libraries are not always required when scripting the DOM. I also wrote for the lucky few who get to write JavaScript code for a single environment (i.e., one browser, mobile browsers, or HTML+CSS+JavaScript-to-native via something like PhoneGap). What you learn in this book may just make a DOM library unnecessary in ideal situationssay, for example, some light DOM scripting for deployment on a WebKit mobile browser only.