how to add multiple classes in javascript code example

Example 1: 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");

Example 2: how to add multiple styles in javascript

Object.assign(yourelement.style,{fontsize:"12px",left:"200px",top:"100px"});

Example 3: add multiple class from array javascript

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