DRY.isEventSupported.js

var isEventSupported = (function(){  

  var TAGNAMES = {
    'select':'input','change':'input',
    'submit':'form','reset':'form',
    'error':'img','load':'img','abort':'img'
  },
  cache = {};
  
  return function isEventSupported(eventName, element) {
    // only return cached result when no element is given
    if (!element && cache[eventName]) {
      return cache[eventName];
    }

    element = element || document.createElement(TAGNAMES[eventName] || 'div');
    eventName = 'on' + eventName;

    // When using `setAttribute`, IE skips "unload", WebKit skips "unload" and "resize", whereas `in` "catches" those
    var isSupported = (eventName in element);

    if (!isSupported) {
      // if it has no `setAttribute` (i.e. doesn't implement Node interface), try generic element
      if (!element.setAttribute) {
        element = document.createElement('div');
      }
      if (element.setAttribute && element.removeAttribute) {
        element.setAttribute(eventName, '');
        isSupported = typeof element[eventName] == 'function';

        // if property was created, "remove it" (by setting value to `undefined`)
        if (typeof element[eventName] != 'undefined') {
          element[eventName] = void 0;
        }
        element.removeAttribute(eventName);
      }
    }

    element = null;
    return (cache[eventName] = isSupported);
  };
})();