addListener

addListener.js

var addListener = (function (window) {
    if (window.addEventListener) {
        return function (el, type, fn) {
            el.addEventListener(type, fn, false);
        };
    }
    if (window.attachEvent) {
        return function (el, type, fn) {
            var f = function () {
                fn.call(el, window.event);
            };
            el.attachEvent('on' + type, f);
        };
    }
    return function (el, type, fn) {
        el['on' + type] = fn;
    };
}(window));

http://blog.livedoor.jp/dankogai/archives/50816979.html