推箱子-根据keycode判断推的方向

<script type="text/javascript">
document.onkeyup=document.onkeydown=function (e) {
//console.log(e);
console.log(e.keyCode);//记录当前按键的键值
//左37,上38,右39,下40
//shift 16
//ctrl 17
//alt 18
//enter 13
if(e.keyCode==37){
$.css(box,"left",$.css(box,"left")-5)
}else if(e.keyCode==38){
$.css(box,"top",$.css(box,"top")-5);
}else if(e.keyCode==39){
$.css(box,"left",$.css(box,"left")+5)
}else if(e.keyCode==40){
$.css(box,"top",$.css(box,"top")+5);
}
}
</script>