JavaScript & DHTML Cookbook

Chapter 4. Variables, Functions, and Flow Control

Introduction

This chapter covers a miscellany of core JavaScript topics. A couple of these recipes (or your own variations on them) may be part of your daily menu. If you don’t use these constructions frequently, let this chapter serve to refresh your memory, and give you models to get you back on track when you need them.

Even simple subjects, such as JavaScript variables and functions, have numerous nuances that are easy to forget over time. A couple of concepts, such as exception handling and the try/catch construction, are also comparatively new in recent browsers. Scripters without formal programming training tend to be rather loose in their attention to detail in the error department—something that can come back to bite you. On the other hand, the browser implementations of some of the details of exception handling are far from compatible. If you aren’t yet using exception-handling techniques in your scripts (perhaps the needs of backward-compatibility prevent it), you should still get to know the concepts. As time goes on and the full W3C DOM becomes implemented in browsers, the notion of “safe scripting” will include regular application of exception-handling practices.

This chapter ends with some suggestions about improving script performance. Most scripts can scrape by with inefficiencies, but larger projects that deal with complex document trees and substantial amounts of hidden data delivered to the client must pay particular ...