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

Deep copy


The function extendCopy(), discussed previously, creates what is called a shallow copy of an object, just like extend2() before that. The opposite of a shallow copy would be, naturally, a deep copy. As discussed previously (in the Heads-up when copying by reference section ), when you copy objects you only copy pointers to the location in memory where the object is stored. This is what happens in a shallow copy. If you modify an object in the copy, you also modify the original. The deep copy avoids this problem.

The deep copy is implemented in the same way as the shallow copy: you loop through the properties and copy them one by one. But, when you encounter a property that points to an object, you call the deep copy function again:

function deepCopy(p, c) {
  c = c || {};
  for (vari in p) {
    if (p.hasOwnProperty(i)) {
      if (typeof p[i] === 'object') {
        c[i] = Array.isArray(p[i]) ? [] : {};
deepCopy(p[i], c[i]);
      } else {
        c[i] = p[i];
      }
    }
  }...