JavaScript CSS how to add and remove multiple CSS classes to an element

Question

How can assign multiple css classes to an html element through javascript without using any libraries?

Answer 1

var el = document.getElementsByClassName('myclass')

el[0].classList.add('newclass');

el[0].classList.remove('newclass');

To find whether the class exists or not, use:

el[0].classList.contains('newclass'); // this will return true or false 

Browser support IE8+