页面倒计时js

function startCountdown(duration, display) {
    let timer = duration, minutes, seconds;
    const intervalId = setInterval(function () {
        minutes = parseInt(timer / 60, 10);
        seconds = parseInt(timer % 60, 10);

        minutes = minutes < 10 ? "0" + minutes : minutes;
        seconds = seconds < 10 ? "0" + seconds : seconds;

        display.textContent = minutes + ":" + seconds;

        if (--timer < 0) {
            clearInterval(intervalId);
            // 倒计时结束后的操作
            alert('倒计时结束！');
        }
    }, 1000);
}

window.onload = function () {
    const duration = 60 * 5; // 设置倒计时时长，这里是5分钟
    const display = document.querySelector('#countdown');
    startCountdown(duration, display);
};

<div id="countdown">00:00</div>