function addEventListener(el, eventName, handler) { if (el.addEventListener) { el.addEventListener(eventName, handler); } else { el.attachEvent('on' + eventName, function(){ handler.call(el); }); } } function forEach(array, fn) { for (i = 0; i < array.length; i++) { fn(array[i], i); } } function toggleClass(el, className) { if (el.classList) { el.classList.toggle(className); } else { var classes = el.className.split(' '); var existingIndex = -1; for (var i = classes.length; i--;) { if (classes[i] === className) { existingIndex = i; } } if (existingIndex >= 0) { classes.splice(existingIndex, 1); } else { classes.push(className); el.className = classes.join(' '); } } } function ready(fn) { if (document.readyState != 'loading'){ fn(); } else if (document.addEventListener) { document.addEventListener('DOMContentLoaded', fn); } else { document.attachEvent('onreadystatechange', function() { if (document.readyState != 'loading') fn(); }); } } function collapsibleMenu(){ var menu = document.getElementsByClassName('collapse'); forEach(menu, function(item, i){ addEventListener(item, 'click', function(){ toggleClass(item, 'open') }); }) } ready(function(){ collapsibleMenu(); });