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java-script / Window Object
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Window Object

The Window object represents the browser window in which a web page is displayed.

It is the top-level (global) object in the Browser Object Model (BOM).
All global JavaScript objects, functions, and variables become members of the window object.

The window object controls the browser window.


Why the Window Object is Important

The Window object allows JavaScript to:

  • Display alert boxes
  • Access browser information
  • Control navigation
  • Manage timers
  • Access other browser objects (history, location, navigator)


Global Scope and Window Object

Any global variable or function becomes a property of window.

var name = "JavaScript";
console.log(window.name);

Global variables belong to window


Common Window Object Methods

1. window.alert()

Displays an alert popup.

window.alert("Welcome to JavaScript");

  • Used for notifications
  • Stops execution until user responds


2. window.confirm()

Displays a confirmation dialog.

let result = window.confirm("Are you sure?");
console.log(result);

Returns true or false


3. window.prompt()

Displays an input dialog.

let userName = window.prompt("Enter your name");
console.log(userName);

Returns user input or null


Console Output Using Window

window.console.log("Hello Console");

  • Used for debugging
  • window keyword is optional


Window Timers

4. setTimeout()

Executes code after a delay.

setTimeout(() => {
    console.log("Executed after 2 seconds");
}, 2000);


5. setInterval()

Executes code repeatedly.

setInterval(() => {
    console.log("Runs every second");
}, 1000);


Window Properties

innerWidth and innerHeight

console.log(window.innerWidth);
console.log(window.innerHeight);

Gets viewport size


location (Access URL)

console.log(window.location.href);


Redirect page

window.location.href = "https://example.com";


Accessing Other Browser Objects via Window

window.history.back();
window.navigator.userAgent;
window.screen.width;

Window is the parent of all BOM objects


Window Object Hierarchy

window
 ├── document
 ├── history
 ├── location
 ├── navigator
 └── screen


Difference Between Window Object and Document Object

FeatureWindow ObjectDocument Object
RepresentsBrowser windowHTML document
Part ofBOMDOM
ControlsBrowser behaviorPage content


Common Use Cases

  • Show alerts and popups
  • Handle browser navigation
  • Set timers
  • Access screen and URL info
  • Debug applications


Two Minute Drill

  • Window represents the browser window
  • It is the top level BOM obect
  • alert, confirm, prompt are window methods
  • Timers are managed by window
  • Other browser objects come under window
  • Global scope belongs to window


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