捕获窗体关闭事件

  window.onbeforeunload = function()
    {
        if(document.body.offsetWidth-50 < event.clientX && event.clientY<0)
        {
            Close();
        }
        else if(event.clientX>document.body.clientWidth && event.clientY<0 ||event.altKey)
        {     
           Close();
        }
    }