JavaScript · DOM and events

classList

Manages classes without touching the class attribute string. Supports add, remove, toggle and contains.

javascriptRunnable example javascript course

Syntax

el.classList.add("active")

Example

Try it

const el = document.createElement("div");
el.classList.add("active");
el.classList.toggle("active");
console.log(el.className);

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.