Checking if an element has a class in vanilla JavaScript

Let's say we have an element:

<button class="primary active">Click me</button>

And we want to check if the element has the active class.

Here's how to do this in two simple steps.

1. Grab the element from the DOM:

   const button = document.querySelector("button");
   

2. Use the element.classList.contains method to check for the class:

   // returns 'true' if the class exists, and 'false' if it doesn't.
   const isActive = button.classList.contains("active");
   

It's really as simple as that!