js 实现倒计时

// 设置倒计时的结束时间，例如从现在开始倒计时10秒
let endTime = new Date().getTime() + 10 * 1000;

// 更新倒计时显示的函数
function updateCountdown() {
    let now = new Date().getTime();
    let distance = endTime - now;

    if (distance < 0) {
        clearInterval(interval);
        document.getElementById("countdown").innerHTML = "倒计时结束";
        return;
    }

    let seconds = Math.floor((distance / 1000) % 60);
    let minutes = Math.floor((distance / 1000 / 60) % 60);
    let hours = Math.floor((distance / (1000 * 60 * 60)) % 24);

    // 补零操作
    hours = hours < 10 ? "0" + hours : hours;
    minutes = minutes < 10 ? "0" + minutes : minutes;
    seconds = seconds < 10 ? "0" + seconds : seconds;

    document.getElementById("countdown").innerHTML = hours + ":" + minutes + ":" + seconds;
}

// 每秒更新倒计时
let interval = setInterval(updateCountdown, 1000);