add to classlist javascript

Add multiple classes to a <div> element:
document.getElementById("myDIV").classList.add("mystyle", "anotherClass", "thirdClass");

Remove a class from a <div> element:
document.getElementById("myDIV").classList.remove("mystyle");

Remove multiple classes from a <div> element:
document.getElementById("myDIV").classList.remove("mystyle", "anotherClass", "thirdClass");

Toggle between two classes for a <div> element:
document.getElementById("myDIV").classList.toggle("newClassName");

Find out if an element has a "mystyle" class:
document.getElementById("myDIV").classList.contains("mystyle");//get array of class names in Javascript
var classesArray = document.getElementById('myElementID').className.split(/\s+/);//get array of classes in Javascript
var classesArray = document.getElementById('myElementID').className.split(/\s+/);

//get array of classes in jQuery
var classesArray = $('#myElementID').attr('class').split(/\s+/);