JavaScript: The Definitive Guide, 6th Edition

Creating Objects

Objects can be created with object literals, with the new keyword, and (in ECMA Script 5 ) with the Object.create() function. The subsections below describe each technique.

Object Literals

The easiest way to create an object is to include an object literal in your JavaScript code. An object literal is a comma-separated list of colon-separated name:value pairs, enclosed within curly braces. A property name is a JavaScript identifier or a string literal (the empty string is allowed). A property value is any JavaScript expression; the value of the expression (it may be a primitive value or an object value) becomes the value of the property. Here are some examples:

var empty = {};                           // An object with no properties
var point = { x:0, y:0 };                 // Two properties
var point2 = { x:point.x, y:point.y+1 };  // More complex values
var book = {                      
    "main title": "JavaScript",           // Property names include spaces,
    'sub-title': "The Definitive Guide",  // and hyphens, so use string literals
    "for": "all audiences",               // for is a reserved word, so quote
    author: {                             // The value of this property is
        firstname: "David",               // itself an object.  Note that
        surname: "Flanagan"               // these property names are unquoted.
    }
};

In ECMAScript 5 (and some ECMAScript 3 implementations), reserved words may be used as property names without quoting. In general, however, property names that are reserved words must be quoted in ECMAScript 3. In ECMAScript 5, a trailing comma following the last property in an object literal ...