Beginning JavaScript

JavaScript is a scripting language that enables you to enhance static web applications by providing dynamic, personalized, and interactive content. This improves the experience of visitors to your site and makes it more likely that they will visit again. You must have seen the flashy drop-down menus, moving text, and changing content that are now widespread on web sites—they are enabled through JavaScript. Supported by all the major browsers, JavaScript is the language of choice on the Web. It can even be used outside web applications—to automate administrative tasks, for example.

This book aims to teach you all you need to know to start experimenting with JavaScript: what it is, how it works, and what you can do with it. Starting from the basic syntax, you'll move on to learn how to create powerful web applications. Don't worry if you've never programmed before—this book will teach you all you need to know, step by step. You'll find that JavaScript can be a great introduction to the world of programming: with the knowledge and understanding that you'll gain from this book, you'll be able to move on to learn newer and more advanced technologies in the world of computing.

In order to get the most out of this book, you'll need to have an understanding of HTML and how to create a static web page. You don't need to have any programming experience.

This book will also suit you if you have some programming experience already, and would like to turn your hand to web programming. You will know a fair amount about computing concepts, but maybe not as much about web technologies.

Alternatively, you may have a design background and know relatively little about the Web and computing concepts. For you, JavaScript will be a cheap and relatively easy introduction to the world of programming and web application development.

Whoever you are, we hope that this book lives up to your expectations.

You'll begin by looking at exactly what JavaScript is, and taking your first steps with the underlying language and syntax. You'll learn all the fundamental programming concepts, including data and data types, and structuring your code to make decisions in your programs or to loop over the same piece of code many times.

Once you're comfortable with the basics, you'll move on to one of the key ideas in JavaScript—the object. You'll learn how to take advantage of the objects that are native to the JavaScript language, such as dates and strings, and find out how these objects enable you to manage complex data and simplify your programs. Next, you'll see how you can use JavaScript to manipulate objects made available to you in the browser, such as forms, windows, and other controls. Using this knowledge, you can start to create truly professional-looking applications that enable you to interact with the user.

Long pieces of code are very hard to get right every time—even for the experienced programmer—and JavaScript code is no exception. You look at common syntax and logical errors, how you can spot them, and how to use the Microsoft Script Debugger to aid you with this task. Also, you need to examine how to handle the errors that slip through the net, and ensure that these do not detract from the experience of the end user of your application.

From here, you'll move on to more advanced topics, such as using cookies and jazzing up your web pages with dynamic HTML and XML. Finally, you'll be looking at a relatively new and exciting technology, remote scripting. This allows your JavaScript in a HTML page to communicate directly with a server, and useful for, say, looking up information on a database sitting on your server. If you have the Google toolbar you'll have seen something like this in action already. When you type a search word in the Google toolbar, it comes up with suggestions, which it gets via the Google search database.

All the new concepts introduced in this book will be illustrated with practical examples, which enable you to experiment with JavaScript and build on the theory that you have just learned. The appendix provides solutions to the exercises included at the end of most chapters throughout the book.

During the first half of the book, you'll also be building up a more complex sample application—an online trivia quiz—which will show you how JavaScript is used in action in a real-world situation.

Paul Wilton started as a Visual Bacic applications programmer at the Ministry of Defense in the UK, then found himself pulled into the Net. Having joined an Intermet development company, he spent three years helping create Internet solutions. He's now running his own successful and rapidly growing company developing online holiday property reservation systems.

Jeremy McPeak began tinkering with web development as a hobby in 1998. Currently working in IT department of a school district, Jeremy has experience developing web solutions with JavaScript, PHP, and C#. He has written several online articles covering topics such as XSLT, WebForms, and C#. He is also co-author of Professional Ajax.