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Objects

Objects in JavaScript can have a literal form (var a = {value: 3}) or a constructed form (var a = new Array()).

Objects are of 6 primitive types:

string
number
boolean
null
undefined
object

Objects are a collection of key/value pairs. The values can be accessed as properties with .propName or ["propName"].

Properties have characteristics that can be controlled with property descriptors such as writable.

var myObject = {
	a: 2
};

Object.getOwnPropertyDescriptor( myObject, "a" );
// {
//    value: 2,
//    writable: true,
//    enumerable: true,
//    configurable: true
// }

Objects can have their mutability modified using Object.freeze(..) or Object.seal(..).

Properties don't have to hold a value, they can be accessors properties with getters/setters.