JAVASCRIPT

add multiple class list at once in js

elem.classList.add("first");
elem.classList.add("second");
elem.classList.add("third");

is equal to :

elem.classList.add("first","second","third");

add multiple class from array javascript

const classArray = ["cl1", "cl2", "cl3"];
div.classList.add(...classArray);

add multiple class from array javascript

document.getElementById("MyElement").className += " MyClass";