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The evolution of JavaScript has been gradual but persistent. Over the course of the past decade, the perception of JavaScript has evolved from a simple toy language into a respected programming language used by corporations and developers across the globe to make incredible applications. The modern JavaScript programming language—as it has always been—is solid, robust, and incredibly powerful. Much of what I’ll be discussing in this book will show what makes modern JavaScript applications so different from what they used to be. Many of the ideas presented in this chapter aren’t new by any stretch, but their acceptance by thousands of intelligent programmers has helped to refine their use and to make them what they are today. So, without further ado, let’s look at modern JavaScript programming.

Objects are the fundamental units of JavaScript. Virtually everything in JavaScript is an object and takes advantage of that fact. However, to build up a solid object-oriented language, JavaScript includes a vast arsenal of features that make it an incredibly unique language, both in possibilities and in style.

When developing code with other programmers, which is standard for most corporate or team projects, it becomes fundamentally important to maintain good authoring practices in order to maintain your sanity. As JavaScript has begun to come into its own in recent years, the amount of JavaScript code developed by professional programmers has increased dramatically. This shift in the perception and use of JavaScript has resulted in important advances in the development practices surrounding it.

Perhaps the most time-consuming process when developing in any programming language is that of testing and debugging your code. With professional-grade code it becomes of the utmost importance to make sure that what you create is fully tested, verifiable, and bug-free. One aspect that makes JavaScript so different from other programming languages is that it isn’t owned or backed by any one company or organization (unlike C#, PHP, Perl, Python, or Java). This difference can make it challenging to have a consistent base with which you can test and debug your code.

Of all the advances made in web development during the past decade, DOM (Document Object Model) scripting is one of the most important techniques that a developer can use to improve the quality of experience for his users.

The most important aspect to unobtrusive DOM scripting is the use of dynamically bound . The ultimate goal of writing usable JavaScript code is to have a web page that will work for the users, no matter what browser they’re using or what platform they’re on. To accomplish this, you set a goal of the features that you want to use, and exclude any browsers that do not support them. For the unsupported browsers, you then give them a functional, albeit less interactive, version of the site. The benefits to writing JavaScript and HTML interactions in this manner include cleaner code, more accessible web pages, and better user interactions. All of this is accomplished by using DOM events to improve the interaction that occurs in web applications.

The interaction between JavaScript and CSS is a mainstay of modern JavaScript programming. It is virtually a requirement that all modern web applications use at least some form of dynamic interaction. When they do, the user is able to move faster and waste less time waiting for pages to load. Combining dynamic techniques with the ideas presented in Chapter 6 on events is fundamental to creating a seamless and powerful user experience.

Forms exist as a means through which structured data can be received from a user, and therefore are immensely useful to a web developer. Inherently, however, there exist very few restrictions upon what a user can do with a form, what data he can enter, or how usable the form is.

A common use of DOM manipulation, traversing, and dynamic CSS manipulation is to create a more responsive experience for the web site end user. One application that benefits from this particular advantage is that of an image gallery (for viewing and browsing images). As browsers have improved in quality, so have dynamic scripts and utilities. Recently, these improvements have lead to a number of high-quality image galleries being released.

A is a term coined by Jesse James Garrett of Adaptive Path to explain the asynchronous client-to-server communication that’s made possible using the XMLHttpRequest object, provided by all modern browsers. Standing for , Ajax is simply a term used to encapsulate the techniques necessary to create a dynamic web application. Additionally, the individual components of the Ajax technique are completely interchangeable—using HTML instead of XML (for example) is perfectly valid.