js倒计时精确到毫秒

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);
        const milliseconds = Math.floor(distance % 1000);

        document.getElementById('countdown').innerHTML = `${days}d ${hours}h ${minutes}m ${seconds}s ${milliseconds}ms`;
    }, 10); // Update every 10 milliseconds for better precision
}

// Set the end time (e.g., 1 hour from now)
const endTime = new Date().getTime() + 3600000;
startCountdown(endTime);