How to loop through a ClassList in JavaScript

When dealing with CSS class names in JavaScript you might find yourself needing to go through each class name in the same selector.

 <div id="testWrapper" class="wrapper background fading"><div>

If we looking to modify each class name we will need to loop through all instances.

So, how can you loop through a ClassList in JavaScript?

There are multiple approaches here. Firstly, we can split each class name by the blank space and convert the result to an Array:

const wrapperElement = document.getElementById('testWrapper')
const classNames = wrapperElement.className.split(' ');

This will give us each class name in an array

From here, we can loop through the class names using forEach(or any array method for that matter):

classNames.forEach(name => {

Additionally, these class names can be accessed using .classList:

const classNames = wrapperElement.classList()

This returns a DOMTokenList like so:

The DOMTokenList interface describes a set of space-separated tokens It can also be iterated through like any standard array:

classNames.forEach(name => {

And there we have it, a straightforwards way to access multiple class names in JavaScript!

Gareth Dunne

Senior JavaScript Engineer and creator of JSdiaries. Passionate about the latest in web technologies and how it can provide value for my clients.