Meaning of '{ }' in javascript

What does assigning a variable to {}, mean? Is that initializing it to a function? I have code in a javascript file that says this

GLGE.Wavefront = f开发者_开发问答unction(uid) {
    GLGE.Assets.registerAsset(this,uid);
    this.multimaterials = [];
    this.materials      = {}; // <---
    this.instances      = [];
    this.renderCaches   = [];
    this.queue          = [];
};

how is that assignment different from an array? Is it a type of array?

What does assigning a variable to {}, mean?

It is an object literal (with no properties of its own).

Is that initializing it to a function?

No, that would be = function () { }.

how is that assignment different from an array?

An array has a bunch of features not found in a basic object, such as .length and a bundle of methods.

Objects are often used to store arbitrary key/value pairs. Arrays are for ordered values.

This is javascript object notation. Particularly {} means empty object, the same as new Object();. See json.org.

That would be an empty JavaScript object.

Using {} creates an object. You can use the object like a hash-map or similar to how you can use arrays in PHP.

var obj = {};
obj['test'] = 'valuehere';
obj.secondWay = 'secondValue';

and you could access them by calling obj.test and obj['secondWay'].

It's an initialized empty object, eg. an object of no particular type. It serves to provide a definition for this.materials so that the code won't have to check it for null or being defined later.

It does create an empty object.

var myObj = {};

Within an object you can define key/value pairs, e.g.:

myObj.color = 'red';

A value can be a function, too:

myObj.getColor = function() { return this.color };

It's JON (Javascript Object Notation) for creating a new empty object. Almost equal in idea to how you'd normally do Object x = new Object() in java, minus the initialization part...