JQuery sample implementation of example scenario in this article: http://gomakethings.com/ditching-jquery-for-vanilla-js/

JQuery-Implementation.js

$(".sandwich").click(function(e) {
	$(e.currentTarget).toggleClass("active");
});

Plain-JS-Implementation.js

// Class Handlers
var hasClass = function (elem, className) {
    return new RegExp(' ' + className + ' ').test(' ' + elem.className + ' ');
}
 
var addClass = function (elem, className) {
    if (!hasClass(elem, className)) {
        elem.className += ' ' + className;
    }
}
 
var removeClass = function (elem, className) {
    var newClass = ' ' + elem.className.replace( /[\t\r\n]/g, ' ') + ' ';
    if (hasClass(elem, className)) {
        while (newClass.indexOf(' ' + className + ' ') >= 0 ) {
            newClass = newClass.replace(' ' + className + ' ', ' ');
        }
        elem.className = newClass.replace(/^\s+|\s+$/g, '');
    }
}

// Sandwich Functions
if ( 'querySelector' in document && 'addEventListener' in window ) {

    var sandwiches = document.querySelectorAll('.sandwich');

    [].forEach.call(sandwiches, function (sandwich) {

        sandwich.addEventListener('click', function(e) {

            if ( hasClass(sandwich, 'active') ) {
                removeClass(sandwich, 'active');
            }

            else {
                addClass(sandwich, 'active');
            }
        
        }
        
    });
    
}