events.js

if (!Element.prototype.addEventListener) {
    var oListeners = {};

    function runListeners(oEvent) {
        if (!oEvent) {
            oEvent = window.event;
        }

        for (var iLstId = 0, iElId = 0, oEvtListeners = oListeners[oEvent.type]; iElId < oEvtListeners.aEls.length; iElId++) {
            if (oEvtListeners.aEls[iElId] === this) {
                for (iLstId; iLstId < oEvtListeners.aEvts[iElId].length; iLstId++) {
                    oEvtListeners.aEvts[iElId][iLstId].call(this, oEvent);
                }

                break;
            }
        }
    }

    Element.prototype.addEventListener = function (sEventType, fListener) {
        if (oListeners.hasOwnProperty(sEventType)) {
            var oEvtListeners = oListeners[sEventType];

            for (var nElIdx = -1, iElId = 0; iElId < oEvtListeners.aEls.length; iElId++) {
                if (oEvtListeners.aEls[iElId] === this) {
                    nElIdx = iElId; break;
                }
            }

            if (nElIdx === -1) {
                oEvtListeners.aEls.push(this);
                oEvtListeners.aEvts.push([fListener]);
                this["on" + sEventType] = runListeners;
            }
            else {
                var aElListeners = oEvtListeners.aEvts[nElIdx];

                if (this["on" + sEventType] !== runListeners) {
                    aElListeners.splice(0);
                    this["on" + sEventType] = runListeners;
                }

                for (var iLstId = 0; iLstId < aElListeners.length; iLstId++) {
                    if (aElListeners[iLstId] === fListener) {
                        return;
                    }
                }

                aElListeners.push(fListener);
            }
        }
        else {
            oListeners[sEventType] = {
                aEls: [this],
                aEvts: [[fListener]]
            };

            this["on" + sEventType] = runListeners;
        }
    };

    Element.prototype.removeEventListener = function (sEventType) {
        if (!oListeners.hasOwnProperty(sEventType)) {
            return;
        }

        var oEvtListeners = oListeners[sEventType];

        for (var nElIdx = -1, iElId = 0; iElId < oEvtListeners.aEls.length; iElId++) {
            if (oEvtListeners.aEls[iElId] === this) {
                nElIdx = iElId;
                break;
            }
        }

        if (nElIdx === -1) {
            return;
        }

        for (var iLstId = 0, aElListeners = oEvtListeners.aEvts[nElIdx]; iLstId < aElListeners.length; iLstId++) {
            aElListeners.splice(iLstId, 1);
        }
    };
}