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

Parasitic inheritance


If you like the fact that you can have all kinds of different ways to implement inheritance in JavaScript, and you're hungry for more, here's another one. This pattern, courtesy of Douglas Crockford, is called parasitic inheritance. It's about a function that creates objects by taking all of the functionality from another object into a new one, augmenting the new object, and returning it, "pretending that it has done all the work".

Here's an ordinary object, defined with an object literal, and unaware of the fact that it's soon going to fall victim to parasitism:

vartwoD = {
name: '2D shape',
dimensions: 2
};

A function that creates triangle objects could:

  • Use twoD object as a prototype of an object called that (similar to this for convenience). This can be done in any way you saw previously, for example using the object() function or copying all the properties.

  • Augment that with more properties.

  • Return that.

    function triangle(s, h) {
    var that = object(twoD);
    that.name ='Triangle...