javascript - 检测到两个键盘按键同时按下

Question

我尝试使用此代码来检测同时按下的两个键盘箭头:

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

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

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

})

但它不管用，无论我多么努力地尝试同时按下它们。

我如何彻底解决此问题并检测两个键何时按下？

Answer 1

每个事件只有一个keyCode。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;
});

(你必须翻到整页才能测试这个片段)