HTML5: The Missing Manual

Appendix B. A Very Short Introduction to JavaScript

There was a time when the Web was all about markup. Pages held text and HTML tags, and not much more. Really advanced websites used server scripts that could tweak the HTML markup before it made its way to the browser, but the code stopped there.

Crack open a web page today and you’re likely to find buckets of JavaScript code, powering everything from vital features to minor frills. Self-completing text boxes, pop-up menus, picture slideshows, and webmail are just a few examples of the many ways crafty developers put JavaScript to work. In fact, it’s nearly impossible to imagine a Web without JavaScript. While HTML is still the language of the Web, Java-Script is now the brains behind its most advanced pages.

In this appendix, you’ll get a heavily condensed JavaScript crash course. This appendix won’t provide a complete tutorial on JavaScript, nor does it have enough information to help you get started if you’ve never written a line of code in any programming language, ever. But if you have some rudimentary programming knowledge—say, you once learned a lick of Visual Basic, picked up the basics of Pascal, or took C out for spin—this appendix will help you transfer your skills to the JavaScript world. You’ll get just enough information to identify familiar programming ingredients like variables, loops, and conditional logic. And you’ll cover all the basic language elements that are used in the JavaScript-based examples in the rest ...