Programming JavaScript Applications

Appendix A. JavaScript Style Guide

You don’t need to know the arcane inner workings of JavaScript in order to do lots of useful things with it. However, if you plan to write an application with tens of thousands of lines of code, you’re going to need to explore a little deeper. Here you’ll explore some fundamentals that will help you build large applications that are still maintainable. For more on these subjects, I strongly recommend JavaScript: The Good Parts by Douglas Crockford.

Example Tests

In the real world, applications are fragile. When you change them, things often break, and you need an easy way to detect those broken things so you can fix them before your users are impacted.

Manual quality assurance is an expensive, time-consuming, and tedious process, and the larger your code base grows, the bigger the job gets. One commonly accepted solution to this problem is to write tests that assure your code does what you expect.

Tests can aid in debugging as well. Frequently when a large number of components interact (often indirectly), it’s difficult to tell which component a bug is hiding in. If you have a test suite, and one component breaks, you’ll be alerted immediately to which component isn’t behaving the way it was designed to behave.

Throughout this book you’ll see QUnit tests in examples to alert you to expected and actual behaviors. QUnit is a JavaScript unit test framework that generates clear, readable test output on whatever page you include it in. It’s the test suite ...