add multiple class in js 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"});