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: What's Object?〕
• Browser's window object. This is the window object in browser. (This is called “host object” in JavaScript.)
• Document Object. This is the object window.document.

Browser Window Object

The browser's window object is the global object. Anything you do with a browser, is done via the window object.

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 JavaScript Variable Scope: Function Level vs Block Level〕

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, because its a global object. 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 JS: Create HTML Element〕
2. Remove element. 〔►see JS: Remove HTML Element〕
3. Change element's attributes. (such as class, id, name, width, etc.) 〔►see JS: Set Element's Attribute Value〕
4. Change element's content. 〔►see JS: Change Element's Content〕
5. Change element's CSS style. 〔►see JS: Change CSS〕

〔►see JS: Basic DOM Methods〕