JS: Browser Window Object, Document Object Model

There are 3 kinds of objects you work with when using JavaScript for website:

• JavaScript Standard Objects and user defined objects. For example, function, array, date, regex, etc. [see JS: Object Type]
• Browser's window object. This is the window object in browser. (This is called “host object” by JavaScript spec.)
• Document Object. This is the object window.document.

Browser Window Object

The browser's window object is the root global object.

Everything is a property of the window object, including:

• JavaScript standard objects [see JS: the Global Object]
• HTML page elements.
• DOM objects.
• Browser's functions and objects.

In browser console, type window to view this object's properties. [see JS: How to Use Browser Console]

When you define a global variable in JavaScript in browser, it becomes a property of the window object. [see JS: var Name Scope]

The window object has important properties. For example:

• window.alert("hi")
• window.open("http://example.com/") [see JS: Open URL window.open(…)]
• window.setTimeout(…) [see JS: Fade a Element]
• window.setInterval(…) [see JS: SVG Clock]
• window.encodeURI(…) [see Encode/Decode URL tutorial]
• window.innerWidth. [see JS: Find Window Size]

• window.localStorage [see JS: Web Storage Tutorial]
• window.history
• window.location [see JS: Get URL (window.location)]

You don't need to prefix window. to use its methods or properties. For example, alert("3") is same as window.alert("3")

The window object also has a property key "window", so window.window refers to itself. and window.window.window, window.window.window.window all refer to window.

The window object and its system is called Browser Object Model (BOM).

Document Object Model (DOM)

One of the most important property of window is window.document. This is the document object.

The document object represent the HTML/XML document in the browser window.

The document object contains methods to manipulate HTML elements and styles. This object system is called DOM (Document Object Model).

The DOM allows you to:

1. Insert element. [see DOM: Create/Insert HTML Element]
2. Remove element. [see DOM: Remove HTML Element]
3. Change element's attributes. (such as class, id, name, width, etc.) [see DOM: Set Element's Attribute Value]
4. Change element's content. [see DOM: Change Element's Content]
5. Change element's CSS style. [see DOM: Change CSS]

[see DOM: Basic DOM Methods]