JavaScript Check If Element Has Class

gistfile1.js

function hasClass(element, className) {
    return element.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(element.className);
}

var myDiv = document.getElementById('MyDiv');

hasClass(myDiv, 'active');

// OR

Element.prototype.hasClass = function(className) {
    return this.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(this.className);
};

document.getElementById('MyDiv').hasClass('active');