同时检测到两个键盘按键被按下 [英] Detecting two keyboard keys being down at the same time

问题描述

我尝试使用此代码来检测同时按下两个键盘箭头:

I tried with this code to detect two keyboard arrows being simultaneously pressed:

document.addEventListener('keydown', event => {

    if (event.keyCode === 38) {
        console.log('up Arrow')
    }

    if (event.keyCode === 39) {
        console.log('right Arrow')
    }

})

但这是行不通的，但是无论我多么努力尝试完全同时按下它们.

But it doesn't work, however hard I try to press them at exactly the same time.

如何彻底解决此问题并检测两个按键何时按下?

How can I cleanly fix this and detect when both keys are down ?

推荐答案

每个事件只有一个keyCode.您必须跟踪向上和向下的键:

There's only one keyCode per event. You have to track the keys going down, and up:

// 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;
});

(您必须进入整页才能测试此代码段)

(you have to go full page to test this snippet)

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