我正在嘗試對游戲進行按鍵檢測，這里的代碼有些起作用，但是問題是它不允許我一次按下我的游戲所需的多個按鍵。它僅允許隨時按下一個鍵并將球移向該方向。有沒有辦法一次允許多次按鍵？var key = 0;var pos = false;var posX = 0;var posY = 0;var jumpSpeed = 4;var ball = new Image();ball.src = 'Ball.png';var canvas = document.getElementById('bg');var ctx = canvas.getContext('2d');document.onkeydown = function (e) {        pos = true;        key = window.event ? e.keyCode : e.which;}document.onkeyup = function (e) {        pos = false;}setInterval(function () {    if (pos == false) return;    else if (key == 65) posX -= 2;    else if (key == 87) posY -= jumpSpeed;    else if (key == 68) posX += 2;}, 1);setInterval(function () {    ctx.drawImage(ball, posX, posY);}, 1);