JavaScript is hot! What started as a quick-and-dirty language created for one of the first web browsers has turned into the world’s most popular programming language. Demand for JavaScript programmers is at an all-time high and only continues to grow.

This book is your key to becoming proficient in the core concepts of JavaScript. Whether your goal is to land a high-paying job as a programmer or to make your own personal website more interactive, you can be confident that the content and techniques presented in this book are fully up to date with the most current JavaScript standards and best practices.

Coupled with engaging and interactive online exercises, each chapter contains complete examples of real code that you can try and test in your own web browser at home.

Just as the only way to Carnegie Hall is to practice, practice, practice, the only way to become a better programmer is to code, code, code!

About This Book

This book is a friendly and approachable guide to getting started with writing JavaScript code. As programming languages go, JavaScript is fairly easy to pick up and start using. Because it’s so accessible, many people who started as web page authors have found themselves in the position of being responsible for maintaining, modifying, and writing JavaScript code. If that describes you, this book will quickly and easily bring you up to speed.

Whether you know a little JavaScript or you’ve never seen it, this book shows you how to write JavaScript the right way.

Topics covered in this book include the following:

• Understanding the basic structures of JavaScript programs
• Integrating JavaScript with HTML5 and CSS3
• Structuring your programs with functions
• Working with JavaScript Objects
• Using advanced JavaScript techniques, such as AJAX, callbacks, and closures
• Getting started with jQuery

Learning JavaScript isn’t only about learning the syntax of the language. It’s also about accessing the tools and community that has been built around the language. Professional JavaScript programmers have greatly refined the tools and techniques used to write JavaScript over the language’s long and exciting history. Throughout the book, we mention important best practices and tools for testing, documenting, and writing better code faster!

To make this book easier to read, keep in mind the following:

• As a convention for this book, all JavaScript code and all HTML and CSS markup appears in monospaced type like this:

  document.write("Hi!");

• The margins on a book page don’t have the same room as your monitor likely does. Therefore, long lines of HTML, CSS, and JavaScript may break across multiple lines. Remember that your computer sees such lines as single lines of HTML, CSS, or JavaScript. We indicate that everything should be on one line by breaking it at a punctuation character or space and then indenting any overage, like so:

  document.getElementById("anElementInTheDocument").
         addEventListener("click",doSomething,false);

• HTML and CSS don’t care very much about whether you use uppercase or lowercase letters or a combination of the two, but JavaScript cares a lot! In order to make sure that you get the correct results from the code examples in the book, always stick to the same capitalizations that we use.

Foolish Assumptions

We have a policy at our company, WatzThis?, to never assume (but, frankly, Eva is better at following the policy than Chris is). If you were ever 12 years old, you’ve probably heard the saying about what happens when you assume. If you don’t know, email us.

You don’t need to be a programming ninja or a hacker to understand programming. You don’t need to understand how the guts of your computer work. You don’t even need to know how to count in binary.

However, we do need to make a couple of assumptions about you. We assume that you can turn your computer on, that you know how to use a mouse and a keyboard, and that you have a working Internet connection and web browser. If you already know something about how to make web pages (it doesn’t take much!), you have a jump start on the material.

The other things you need to know to write and run JavaScript code are details we cover in this book. And the one thing you’ll find to be true is that programming requires attention to details.

Icons Used In This Book

Here’s a list of the icons we use in this book to flag text and information that’s especially noteworthy:

This icon highlights helpful tips that show you easy ways or shortcuts that will save you time or effort.

Whenever you see this icon, pay special attention. You won’t want to forget the information you’re about to read.

Be careful — very careful. This icon warns you of pitfalls to avoid.

This icon highlights the great exercises you can find on the website. If you’re interested in trying your hand at JavaScript, go online and visit www.dummies.com/go/codingwithjavascript.

This icon highlights technical details that you may or may not find interesting. Feel free to skip this information, but if you’re the techie type, you might enjoy reading it.

Beyond the Book

Here’s where you can find the online content for this book:

• Exercises: You can find all the exercises online by going to www.dummies.com/go/codingwithjavascript to access the exercises at Codeacademy.
• Examples: You can find all the examples in the chapters at www.dummies.com/go/codingwithjavascript. Here you will find a directory labeled by chapter. Within the chapter, you will find each example labeled by its listing number
• Cheat Sheet: You can find lists of useful information at www.dummies.com/cheatsheet/codingwithjavascript.
• Extras: You can even find additional articles related to each part of the book. You can access this extra content at www.dummies.com/extras/codingwithjavascript.
• Updates: From time to time, we will need to make updates to a book. Code and specifications are constantly changing, so the commands and syntax that work today may not work tomorrow. You can find this information at www.dummies.com/extras/codingwithjavascript.

Where to Go from Here

Coding with JavaScript is fun, and once you get a little knowledge under your belt, the world of interactive web applications is your oyster! So buckle up! We hope you enjoy the book and our occasional pearls of wisdom.