Book Image

Object-Oriented JavaScript - Second Edition - Second Edition

Book Image

Object-Oriented JavaScript - Second Edition - 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

JSON


The JSON object is new to ES5. It's not a constructor (similarly to Math) and has only two methods: parse() and stringify(). For ES3 browsers that don't support JSON natively, you can use the "shim" from http://json.org.

JSON stands for JavaScript Object Notation. It's a lightweight data interchange format. It's a subset of JavaScript that only supports primitives, object literals, and array literals.

Members of the JSON object

Method

Description

parse(text, callback)

Takes a JSON-encoded string and returns an object:

> var data = '{"hello": 1, "hi": [1, 2, 3]}';
> var o = JSON.parse(data);
> o.hello;
1
> o.hi;
[1, 2, 3]

The optional callback lets you provide your own function that can inspect and modify the result. The callback takes key and value arguments and can modify the value or delete it (by returning undefined).

> function callback(key, value) {
    console.log(key, value);
    if (key === 'hello') {
      return 'bonjour';
    }
    if (key === 'hi') {
      return undefined;
    }
    return value;
  }

>   var o = JSON.parse(data, callback);
hello 1
0 1
1 2
2 3
hi [1, 2, 3]
Object {hello: "bonjour"}
> o.hello;
"bonjour"
> 'hi' in o;
false

stringify(value, callback, white)

Takes any value (most commonly an object or an array) and encodes it to a JSON string.

> var o = {
    hello: 1, 
    hi: 2, 
    when: new Date(2015, 0, 1)
  };

> JSON.stringify(o);
"{"hello":1,"hi":2,"when":"2015-01-01T08:00:00.000Z"}"

The second parameter lets you provide a callback (or a whitelist array) to customize the return value. The whitelist contains the keys you're interested in:

JSON.stringify(o, ['hello', 'hi']);
"{"hello":1,"hi":2}"

The last parameter helps you get a human-readable version. You specify the number of spaces as a string or a number.

> JSON.stringify(o, null, 4);
"{
"hello": 1,
"hi": 2,
"when": "2015-01-01T08:00:00.000Z"
}"