javascript keycode大全&addeventhandler键盘监听事件

   document.addEventListener('keydown', function(e) {
      console.log(e.keyCode);
    }, false);

keycode   37 = Left
keycode   38 = Up
keycode   39 = Right
keycode   40 = Down

参考：https://www.cnblogs.com/exmyth/p/3510560.html

removeEventListener:https://blog.csdn.net/weixin_33941350/article/details/91384546

                                   https://www.cnblogs.com/lxg0/p/6568910.html