部分代码如下:
  onkey :function(ev){
ev = (ev)?ev:((window.event)?window.event:" ")
keyCode = ev.keyCode?ev.keyCode:(ev.which?ev.which:ev.charCode);

        switch(keyCode){
        case 37://left
            this._onleft(ev);
            break;
        case 38://up
            this._onup(ev);
            break;
        case 39://right
            this._onright(ev);
            break;
        case 40://down
            this._ondown(ev);
            break;
        }
    },