add classname + number code example

Example 1: js add class

// getting the target element
var myElement = document.querySelector('#myElement');

// example for addding some-class to the element
myElement.classList.add('some-class');

// multiple classes can be added like this
myElement.classList.add('one-class', 'one-more-class');

// example for removing any class from the element
myElement.classList.remove('any-class');

Example 2: javascript add class to element

var someElement= document.getElementById("myElement");
    someElement.className += " newclass";//add "newclass" to element (space in front is important)