兼容性的事件处理程序

事件监听

function addEvent(target,type,handler) {
    if(target.addEventListener){
        target.addEventListener(type,handler,false)
    }else {
        target.attachEvent("on"+type,
                            function (event) {
                                return handler.call(target,event)
                            }
        )
    }
}

取消默认事件

function cancelHandler(event) {
    var event = event || window.event;
    if(event.preventDefault){event.preventDefault();}
    if(event.returnValue){event.returnValue = false;}
    
    return false;
}