简单的使用键盘操控div移动

<script>
    window.onload=function () {

        var box = document.getElementsByClassName("box")[0];
        var left = 0;
        var top = 0;
        document.onkeydown = function (ev) {
            var oEvent = window.event || ev;
            // alert(oEvent.keyCode)
            switch (oEvent.keyCode) {
                case 37:
                    left -= 10;
                    box.style.left = left + "px";
                    break;
                case 38:
                    top -= 10;
                    box.style.top = top + "px";
                    break;
                case 39:
                    left += 10;
                    box.style.left = left + "px";
                    break;
                case 40:
                    top += 10;
                    box.style.top = top + "px";
                    break;
            }
        }
    }
</script>