JavaScript Patterns 3.5 JSON

JSON: JavaScript Object Notation

{"name": "value", "some": [1, 2, 3]} 

The only syntax difference between JSON and the object literal is that property names need to be wrapped in quotes to be valid JSON. In object literals the quotes are required only when the property names are not valid identifiers, for example, they have spaces {"first name": "Dave"}.

In JSON strings you cannot use functions or regular expression literals.

Working with JSON

JSON.parse()

use the JSON.parse()method, which is part of the language since ES5 and is natively provided by the JavaScript engines in modern browsers.

For older JavaScript engines, you can use the JSON.org library (http://www.json.org/json2.js) to gain access to the  JSON object and its methods.

// an input JSON string

var jstr = '{"mykey": "my value"}'; 

// antipattern

var data = eval('(' + jstr + ')'); 

// preferred

var data = JSON.parse(jstr);

console.log(data.mykey); // "my value" 

using YUI3

// an input JSON string

var jstr = '{"mykey": "my value"}'; 

// parse the string and turn it into an object

// using a YUI instance

YUI().use('json-parse', function (Y) {

    var data = Y.JSON.parse(jstr);

    console.log(data.mykey); // "my value"

}); 

using JQuery

// an input JSON string

var jstr = '{"mykey": "my value"}';

var data = jQuery.parseJSON(jstr);

console.log(data.mykey); // "my value" 

JSON.stringify()

var dog = {

    name: "Fido",

    dob: new Date(),

    legs: [1, 2, 3, 4]

};

var jsonstr = JSON.stringify(dog);

// jsonstr is now:

// {"name":"Fido","dob":"2010-04-11T22:36:22.436Z","legs":[1,2,3,4]}