append class to div javascript code example
Example 1: js add class
var element = document.getElementById('element');
element.classList.add('class-1');
element.classList.add('class-2', 'class-3');
element.classList.remove('class-3');
Example 2: add class to html tag javascript
var root = document.getElementsByTagName( 'html' )[0]; // '0' to assign the first (and only `HTML` tag)
root.className += ' responsive';