We use classList and className on JavaScript DOM to manipulate classes from the element. These two DOM property has different use cases. Let's see what is the main difference between them.

classList

• Using classList, you can add or remove a class without affecting any other classes the element may have.

• So this is helpful for adding additional classes to an element that contain other classes.

• classList has some handy methods like toggle and replace.

if (clicked) {
    button.classList.add('clicked');
} else {
    button.classList.remove('clicked');
}

Here if the button was clicked it will add the clicked class along with other classes the element may have and it will remove only the clicked class from the element.

className

• If you use className, it will wipe out any existing classes while adding the new one (or if you assign an empty string it will wipe out all of them).

• Using className can be a convenience when you know this element will not use any other classes.

if (clicked) {
    button.className = 'clicked';
} else {
    button.className = '';
}

In this case, className will wipe all the classes the element may have and add clicked class to it. The empty string('') will wipe all the classes.

Conclusion

• My recommendation would be to use className whenever possible.

• Use classList when you need classList methods like toggle, replace, etc.