How to add CSS class using JavaScript

Adding CSS class dynamically by using .className property in JavaScript


In this tutorial, I am going to explain the procedure of adding the CSS class using JavaScript. The need for adding CSS by JavaScript is that sometimes, we need to add style in a dynamic manner, which means that styling should kick in upon the user interaction. Inline style rules of CSS do not fulfill this requirement of dynamic styling.

I will be using the .className property to deploy the dynamic interaction on the web-page. The .className property can be used to retrieve or set a class to the HTML element.

For retrieving the class we can use:


While for setting a new class we have to use:

HTMLElementObject.className = class


<!DOCTYPE html>
<html lang="en">
<meta charset="utf-8">
<title>setProperty() Method using JavaScript </title>
 width: 50%;
 margin: 0px auto;

 .addCSS {
          color: blue;
          font-size: 3.0rem;

   <div class="main-div">
      Setting className property using JavaScript

     <p id = "text-data">
      Hello World!

   <button onclick = "addClass()">
     function addClass() {
       var addelement = document.getElementById("text-data");
       addelement.className += "addCSS";



Before Clicking the Button

After Clicking the Button

I hope with the above tutorial, you have learned the dynamic styling by using CSS with JavaScript.

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