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An object is a great way to keep track of a bunch of related information. Additionally, the information contained in one object can be "inherited" by another. For example, imagine a program which represents cars. Other languages like PHP, Java, or C++ force the programmer to act as a manufacturer, providing a blueprint with every detail of how each vehicle's parts will work before it ever runs. But JavaScript lets you add and remove parts as needed, so you can have a Ferrari one second and a seaplane the next. And if at some point you particularly like the current arrangement, you can instantly make unlimited copies.

Syntax[]

Main article: Object#Literal_syntax

Objects are initialized via braces {}; they may be populated either during initialization or later. The following examples are effectively identical:

var obj = {foo: 'bar'};


var obj = {};
obj.foo = 'bar';

If a property is accessed before being initialized, its value is undefined.