How to Change the Class of an Element Using JavaScript

890 views 1 year ago Javascript

Use the `classList` Property

In modern browsers you can use the DOM element's classList property to add, remove or toggle CSS classes to the HTML elements dynamically with JavaScript.

The following example will show you how to change the class of a DIV element onclick of the button. It works all major browsers such as Chrome, Firefox, Microsoft Edge, Safari, etc.

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Change an Element's Class with JavaScript</title>
<style>
    .highlight{
        background: yellow;
    }
    .bordered{        
        border: 5px solid #000;
    }
    .padded{
        padding: 20px;
    }
    .hide{
        display: none;
    }
</style>
</head>
<body>
    <div id="content">
        <h1>This is a heading</h1>
        <p>This is a paragraph of text.</p>
    </div>
    <p>
        <button type="button" onclick="addSingleClass()">Add Highlight Class</button>
        <button type="button" onclick="addMultipleClass()">Add Bordered and Padded Class</button>        
    </p>
    <p>
        <button type="button" onclick="removeSingleClass()">Remove Highlight Class</button>  
        <button type="button" onclick="removeMultipleClass()">Remove Bordered and Padded Class</button>
    </p>
    <p>
        <button type="button" onclick="toggleClass()">Toggle Hide Class</button>
    </p>
    <script>
        // Selecting element
        var elem = document.getElementById("content");
        function addSingleClass(){
            elem.classList.add("highlight");  // Add a highlight class
        }        
        function addMultipleClass(){
            elem.classList.add("bordered", "padded");  // Add bordered and padded class
        }
        function removeSingleClass(){
            elem.classList.remove("highlight");  // Remove highlight class
        }
        function removeMultipleClass(){
            elem.classList.remove("bordered", "padded");  // Remove bordered and padded class
        }
        function toggleClass(){
            elem.classList.toggle("hide");  // Toggle hide class
        }
    </script>
</body>
</html>

Alternatively, to support older browsers you can use the className property. The following example demonstrates how to add or replace CSS classes using this property.

<div id="info">Some important information!</div>
<script>
// Selecting element
var elem = document.getElementById("info");
elem.className = "note";  // Add or replace all classes with note class
elem.className += " highlight";  // Add a new class highlight
elem.className += " bordered padded";  // Add two new classes bordered and padded
elem.className = ""; // Remove all classes
</script>

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