71: JavaScript Windows

blanchloe profile image Seonyoung Chloe ・2 min read

The Browser Object Model (BOM) allows JavaScript to "talk to" the browser.

The Window interface represents a window containing a DOM document; the document property points to the DOM document loaded in that window. A window for a given document can be obtained using the document.defaultView property.

A global variable, window, representing the window in which the script is running, is exposed to JavaScript code.

The Window interface is home to a variety of functions, namespaces, objects, and constructors which are not necessarily directly associated with the concept of a user interface window. However, the Window interface is a suitable place to include these items that need to be globally available. Many of these are documented in the JavaScript Reference and the DOM Reference.

In a tabbed browser, each tab is represented by its own Window object; the global window seen by JavaScript code running within a given tab always represents the tab in which the code is running. That said, even in a tabbed browser, some properties and methods still apply to the overall window that contains the tab, such as resizeTo() and innerHeight. Generally, anything that can't reasonably pertain to a tab pertains to the window instead.

The Browser Object Model (BOM)

There are no official standards for the Browser Object Model (BOM).

Since modern browsers have implemented (almost) the same methods and properties for JavaScript interactivity, it is often referred to, as methods and properties of the BOM.

The Window Object

The window object is supported by all browsers. It represents the browser's window.

All global JavaScript objects, functions, and variables automatically become members of the window object.

Global variables are properties of the window object.
Global functions are methods of the window object.

Even the document object (of the HTML DOM) is a property of the window object:


is equal to


1) MDN
2) W3schools

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