AJAX has quickly pushed JavaScript into the foreground as an integral part of the Web 2.0 application experience. One side-effect of JavaScript's re-emergence has been its reevaluation by web developers as a first-class programming environment. What they'd before dismissed as mere glue code underlying the likes of roll-overs and form validation has turned out to be an elegant, mature, powerful language running on the Web itself. JavaScript is a functional language. It incorporates powerful object-oriented development thanks to the flexibility of prototype-based inheritance. Let Willison re-introduce you to JavaScript: from building your own classes to taking advantage of the functional programming style, prototype-based object orientation, useful JavaScript idioms, and avoiding memory leaks. This ain't your 1995 JavaScript.