js活动剩余时间倒计时

function startCountdown(endTime) {
    const interval = setInterval(() => {
        const now = new Date().getTime();
        const distance = endTime - now;

        if (distance < 0) {
            clearInterval(interval);
            document.getElementById('countdown').innerHTML = "EXPIRED";
            return;
        }

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

        document.getElementById('countdown').innerHTML = `${days}d ${hours}h ${minutes}m ${seconds}s`;
    }, 1000);
}

// 假设活动结束时间为2023年12月31日23时59分59秒
const deadline = new Date('2023-12-31T23:59:59').getTime();
startCountdown(deadline);

function getServerTime() {
    // 这里应该是一个AJAX请求获取服务器时间
    return new Date().getTime(); // 示例代码，实际应替换为真实请求
}

setInterval(() => {
    const serverTime = getServerTime();
    startCountdown(endTime, serverTime);
}, 60000); // 每分钟同步一次服务器时间

window.onload = function() {
    const storedTime = localStorage.getItem('countdownTime');
    if (storedTime) {
        const remainingTime = parseInt(storedTime, 10) - new Date().getTime();
        startCountdown(remainingTime + new Date().getTime());
    } else {
        startCountdown(endTime);
    }
};

function startCountdown(remainingTime) {
    const interval = setInterval(() => {
        const now = new Date().getTime();
        const distance = remainingTime - now;

        if (distance < 0) {
            clearInterval(interval);
            localStorage.removeItem('countdownTime');
            document.getElementById('countdown').innerHTML = "EXPIRED";
            return;
        }

        localStorage.setItem('countdownTime', distance.toString());
        // 更新显示
        const days = Math.floor(distance / (1000 * 60 * 60 * 24));
        const hours = Math.floor((distance % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));
        const minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
        const seconds = Math.floor((distance % (1000 * 60)) / 1000);

        document.getElementById('countdown').innerHTML = `${days}d ${hours}h ${minutes}m ${seconds}s`;
    }, 1000);
}