Introducing order to Ajax

This chapter covers

■Developing and maintaining large Ajax client codebases

■Refactoring Ajax JavaScript code

■Exploring common design patterns used in Ajax applications

■Using Model-View-Controller on the server side of an Ajax app

■Overview of third-party Ajax libraries

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70CHAPTER 3

Introducing order to Ajax

In chapter 2, we covered all the basic technologies that make up an Ajax application. With what we’ve learned so far, it’s possible to build that super-duper Ajaxpowered web application that you’ve always dreamed of. It’s also possible to get into terrible trouble and end up with a tangle of code, HTML markup, and styling that is impossible to maintain and that mysteriously stops working one day. Or worse, you end up with an application that continues to work so long as you don’t breathe near it or make a sudden loud noise. To be in such a situation on a personal project can be disheartening. To be in such a situation with an employer’s or paying customer’s site—someone who wants a few tweaks here and there—can be positively frightening.

Fortunately, this problem has been endemic since the dawn of computing— and probably before that! People have developed ways to manage complexity and to keep increasingly large codebases in working order. In this chapter, we’ll introduce the core tools for keeping on top of your code, allowing you to write and rewrite your Ajax application to your customer’s heart’s content, and still go home from work on time.

Ajax represents a break from the previous use of DHTML technologies not only in the way the technologies are put together but also in the scale at which they are used. We’re dealing with much more JavaScript than a classic web application would, and the code will often be resident in the browser for a much longer time. Consequently, Ajax needs to manage complexity in a way that classic DHTML doesn’t.

In this chapter, we’ll give an overview of the tools and techniques that can help you keep your code clean. These techniques are most useful, in our experience, when developing large, complex Ajax applications. If you want to write only simple Ajax applications, then we suggest you skip ahead to the example-driven chapters, starting with chapter 9. If you already know refactoring and design patterns back to front, then you may wish to skim this chapter and move on to the application of these techniques to Ajax in chapters 4 through 6. Even so, the groundwork that we lay here is important in adapting these approaches to JavaScript, so we expect you’ll return here at some point. We also take the opportunity at the end of this chapter to review the current state of third-party libraries for Ajax, so if you’re shopping for frameworks to streamline your project, you may want to check out section 3.5.