Summary: in this tutorial, you will learn about the JavaScript window object which is the global object of JavaScript in the browser and exposes the browser’s functionality.

The window object is global

The global object of JavaScript in the web browser is the window object. It means that all variables and functions declared globally with the var keyword become the properties and methods of the window object. For example:

Code language: JavaScript (javascript)

Output:

Because the counter variable and the showCounter() function are declared globally with the var keyword, they are automatically added to the window object.

If you don’t want to pollute the window object, you can use the let keyword to declare variables and functions.

The window object exposes the browser’s functionality

The window object exposes the functionality of the web browser to the webpage.

1) Window size

The window object has four properties related to the size of the window:

• The innerWidth and innerHeight properties return the size of the page viewport inside the browser window (not including the borders and toolbars).
• The outerWidth and outerHeight properties return the size of the browser window itself.

Also, document.documentElement.clientWidth and document.documentElement.clientHeight properties indicate the width and height of the page viewport.

To get the size of the window, you use the following snippet:

Code language: JavaScript (javascript)

2) Open a new window

To open a new window or tab, you use the window.open() method:

Code language: CSS (css)

The window.open() method accepts three arguments: the URL to load, the window target and a string of window features.

The third argument is a command-delimited string of settings specifying displaying information for the new window such as width, height, menubar, and resizable.

The window.open() method returns a WindowProxy object, which is a thin wrapper of the window object. In case the new window cannot be opened, it returns null.

For example, to open a new window that loads the page about.html at localhost, you use the following code:

Code language: JavaScript (javascript)

The code opens the page about.html in a new tab. If you specify the height and width of the window, it will open the URL in a new separated window instead of a new tab:

Code language: JavaScript (javascript)

To load another URL on an existing window, you pass an existing window name to the window.open() method. The following example loads the contact.html webpage to the contact window:

Code language: JavaScript (javascript)

Put it all together. The following code opens a new window that loads the webpage about.html and then after 3 seconds, it loads the webpage contact.html in the same window:

Code language: JavaScript (javascript)

3) Resize a window

To resize a window you use the resizeTo() method of the window object:

Code language: JavaScript (javascript)

The following example opens a new window that loads the http://localhost/js/about.html page and resize it to (600,300) after 3 seconds:

Code language: JavaScript (javascript)

The window.resizeBy() method allows you to resize the current window by a specified amount:

Code language: JavaScript (javascript)

For example:

Code language: JavaScript (javascript)

4) Move a window

To move a window to a specified coordinate, you use the moveTo() method:

Code language: JavaScript (javascript)

In this method, x and y are horizontal and vertical coordinates to be moved to. The following example opens a new window and moves it to (0,0) coordinate after 3 seconds:

Code language: JavaScript (javascript)

Similarly, you can move the current window by a specified amount:

Code language: JavaScript (javascript)

5) Close a window

To close a window, you use the window.open() method:

Code language: JavaScript (javascript)

The following example opens a new window and closes it after 3 seconds:

Code language: JavaScript (javascript)

6) The window.opener property

A newly created window can reference back to the window that opened it via the window.opener property. This allows you to exchange data between the two windows.

Summary

• The window is the global object in the web browser.
• The window object exposes the functionality of the web browser.
• The window object provides methods for manipulating a window such as open(), resize(), resizeBy(), moveTo(), moveBy(), and close().