//add_event
function addEvent(oElement, sEvType, fnHandler, bUseCapture){
    if (oElement.addEventListener){
        oElement.addEventListener(sEvType, fnHandler, bUseCapture);
        return true;
    }
    else if (oElement.attachEvent){
        oElement.attachEvent('on' + sEvType, fnHandler);
    }
    else
       oElement['on' + sEvType] = fnHandler;
       
}
    
function removeEvent(oElement, sEvType, fnHandler, bUseCapture) {
    if (oElement.removeEventListener) {
        oElement.removeEventListener(sEvType, fnHandler, bUseCapture);
    }
    else if (oElement.detachEvent) {
        oElement.detachEvent("on" + sEvType, fnHandler);
    }
    else oElement["on" + sEvType] = null;
}