JavaScript: Get the width and height of a window online

Last update on July 18 2025 13:00:07 (UTC/GMT +8 hours)

JavaScript DOM: Exercise-13 with Solution

Window Resize Dimensions

Write a JavaScript program to get the window width and height (any time the window is resized).

Sample Solution:

HTML Code:

<!-- Declaration of HTML document type -->
<!DOCTYPE html>
<!-- Start of HTML document -->
<html>
<!-- Start of head section -->
<head>
<!-- Declaring character encoding -->
<meta charset=utf-8 />
<!-- Setting title of the document -->
<title>Window Size : height and width</title>
<!-- End of head section -->
</head>
<!-- Comment indicating to resize the window and see the result -->
<!-- Resize the window (here output panel) and see the result !-->
<!-- Start of body section with onload and onresize events -->
<body onload="getSize()" onresize="getSize()">
<!-- Division to display height and width size -->
<div id="wh"> 
    <!-- Place height and width size here! --> 
</div>
<!-- End of body section -->
<body>
</body>
<!-- End of HTML document -->
</html>

JavaScript Code:

// Function declaration for getSize
function getSize()
{
    // Getting the width of the viewport
    var w = document.documentElement.clientWidth;
    // Getting the height of the viewport
    var h = document.documentElement.clientHeight;
        
    // Put the result into a h1 tag
    document.getElementById('wh').innerHTML = "<h1>Width: " + w + " • Height: " + h + "</h1>";
}

output:

Flowchart:

Live Demo:

See the Pen javascript-dom-exercise-13 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

Write a JavaScript function that continuously displays the current window width and height in real time as the window is resized.
Write a JavaScript function that updates a dedicated paragraph with the new window dimensions each time the window is resized.
Write a JavaScript function that throttles the window resize event to update the dimensions only every 500ms.
Write a JavaScript function that logs the window dimensions to the console every time a resize event occurs, ensuring performance optimization.

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