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Event Listener polyfill
// addEventListener polyfill IE6+
!window.addEventListener && (function (window, document) {
function Event(e, element) {
var instance = this;
for (property in e) {
instance[property] = e[property];
}
instance.currentTarget = element;
instance.target = e.srcElement || element;
instance.timeStamp = +new Date;
instance.preventDefault = function () {
e.returnValue = false;
};
instance.stopPropagation = function () {
e.cancelBubble = true;
};
}
function addEventListener(type, listener) {
var
element = this,
listeners = element.listeners = element.listeners || [],
index = listeners.push([listener, function (e) {
listener.call(element, new Event(e, element));
}]) - 1;
element.attachEvent('on' + type, listeners[index][1]);
}
function removeEventListener(type, listener) {
for (var element = this, listeners = element.listeners || [], length = listeners.length, index = 0; index < length; ++index) {
if (listeners[index][0] === listener) {
element.detachEvent('on' + type, listeners[index][1]);
}
}
}
window.addEventListener = document.addEventListener = addEventListener;
window.removeEventListener = document.removeEventListener = removeEventListener;
if ('Element' in window) {
Element.prototype.addEventListener = addEventListener;
Element.prototype.removeEventListener = removeEventListener;
} else {
var
head = document.getElementsByTagName('head')[0],
style = document.createElement('style');
head.insertBefore(style, head.firstChild);
style.styleSheet.cssText = '*{-ms-event-prototype:expression(!this.addEventListener&&(this.addEventListener=addEventListener)&&(this.removeEventListener=removeEventListener))}';
}
})(window, document) && scrollBy(0, 0);

matthewp commented Jul 5, 2012

This won't work when the listener is an object. In that case addEventListener will call listener.handleEvent. Should be easy enough to fix though. Here's an explanation:

http://ajaxian.com/archives/an-alternative-way-to-addeventlistener

Thanks for this polyfill - the CSS expression stuff is a stroke of genius. I've forked it to use it in a project of my own (you don't specify a license but I assume that's kosher...).

There's one bit I don't quite understand: what's up with scrollBy(0, 0)? The IIFE returns undefined, so the && operator short-circuits and the code is never reached. What does it do?

Keep in mind, for...in loops are supported by IE10+. So this polyfill will not work unless you replace then with normal for(;;) loops.

will this work on DOMContentLoaded, readystatechange, progress or what?

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