Book Image

Object-Oriented JavaScript - Second Edition

Book Image

Object-Oriented JavaScript - Second Edition

Overview of this book

JavaScript is the behavior, the third pillar in today's paradigm that looks at web pages as something that consists of clearly distinguishable parts: content (HTML), presentation (CSS) and behavior (JavaScript). Using JavaScript, you can create not only web pages but also desktop widgets, browser and application extensions, and other pieces of software. It's a pretty good deal: you learn one language and then code all kinds of different applications. While there's one chapter specifically dedicated to the web browser environment including DOM, Events and AJAX tutorials, the rest is applicable to the other environments Many web developers have tried coding or adopting some bits of JavaScript, but it is time to "man up" and learn the language properly because it is the language of the browser and is, virtually, everywhere. This book starts from zero, not assuming any prior JavaScript programming knowledge and takes you through all the in-depth and exciting futures hidden behind the facade. Once listed in the "nice to have" sections of job postings, these days the knowledge of JavaScript is a deciding factor when it comes to hiring web developers. After reading this book you'll be prepared to ace your JavaScript job interview and even impress with some bits that the interviewer maybe didn't know. You should read this book if you want to be able to take your JavaScript skills to a new level of sophistication.
Table of Contents (19 chapters)
Object-Oriented JavaScript Second Edition
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Built-in Functions
Regular Expressions
Index

Variables


Variables are used to store data; they are placeholders for concrete values. When writing programs, it's convenient to use variables instead of the actual data, as it's much easier to write pi instead of 3.141592653589793, especially when it happens several times inside your program. The data stored in a variable can be changed after it was initially assigned, hence the name "variable". You can also use variables to store data that is unknown to you while you write the code, such as the result of a later operation.

Using a variable requires two steps. You need to:

  • Declare the variable

  • Initialize it, that is, give it a value

To declare a variable, you use the var statement, like this:

var a;
var thisIsAVariable; 
var _and_this_too; 
var mix12three;

For the names of the variables, you can use any combination of letters, numbers, the underscore character, and the dollar sign. However, you can't start with a number, which means that this is invalid:

var 2three4five;

To initialize a variable...