我正在自学javascript，并有一个div，每次按下空格键时它都会在屏幕上移动。但是每次按下空格键时速度都会增加，我很困惑为什么会这样，我错过了什么来保持速度恒定？

window.addEventListener('keydown', (event) => {
        switch (event.key) {
        case ' ':
        if (posLeft > canvasWidth - 100 || Rocket.style.visibility != 'hidden') {
            Rocket.style.visibility = 'hidden'
        }
        else {
            Rocket.style.visibility = 'visible';
            console.log(posLeft);
            Rocket.style.left = (Player.offsetLeft + Player.offsetWidth) + 'px';
            Rocket.style.top = (Player.offsetTop + Player.offsetHeight / 2.5) + 'px';
            setInterval(function () {
                if (rocketLeft < canvasWidth) {
                    rocketLeft++;
                    console.log(rocketLeft);
                    Rocket.style.left = parseInt(Rocket.style.left, 10) + 1 + 'px';
                }
            });
            rocketLeft = 0;
            break;
        }
        };
        });