检测两个键盘键同时关闭

但它不起作用,但我努力尝试在同一时间按它们.

如何干净地修复此问题并检测两个键何时关闭？

keyCode每个活动只有一个.您必须跟踪向下和向上的键:

// if you keep both up and down keys down, you'll get a message
let downKeys = {}; // the set of keys currently down
document.addEventListener('keydown', event => {
    downKeys[event.keyCode] = true;
    if (downKeys[38] && downKeys[40]) {
       console.log("both down!");
    }
});
document.addEventListener('keyup', event => {
    downKeys[event.keyCode] = false;
});