Scriptin’ with JavaScript and Ajax: A Designer’s Guide

Chapter 4. Events

In a modern web site or browser-based application, JavaScript’s primary purpose is to provide responses to the user interactions with the interface, or to be more technically precise, to handle events that are triggered by user actions.

Events are messages that the browser fires off in a constant stream as the user works; for example, every time the user moves the pointer over an HTML element, clicks the mouse, or moves the cursor into a field of a form, a corresponding event message is fired. JavaScript receives these messages, but does nothing unless you provide an event handler that provides a response to them.

Your ability to write code that can monitor and respond to the events that matter to your application is key to ...