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HTML

              
                <div id="countdown"></div>
              
            
!

CSS

              
                
              
            
!

JS

              
                let targetDate = new Date(); // 現在の日時を取得
targetDate.setDate(targetDate.getDate()+1); // 明日に設定
targetDate.setHours(0, 0, 0, 0); // 0時に設定

let totalSeconds = calculateRemainingSeconds(targetDate);
let count = totalSeconds;
let countdownInterval = setInterval(countdown, 1000);

// カウントダウン関数
function countdown() {
    let hours = Math.floor(count / 3600);
    let minutes = Math.floor((count % 3600) / 60);
    let seconds = count % 60;

    let formattedTime = formatTime(hours) + ":" + formatTime(minutes) + ":" + formatTime(seconds);

    document.getElementById('countdown').innerHTML = formattedTime;

    if (count <= 0) {
        clearInterval(countdownInterval);
        endFunction();
    } else {
        count--;
    }
}

// 0になった時の関数
function endFunction() {
    document.getElementById('countdown').innerHTML = 'END';
}

// 明日の0時までの残り秒数を計算する関数
function calculateRemainingSeconds(targetDate) {
    let now = new Date();
    let tomorrow = new Date(targetDate);
    tomorrow.setDate(tomorrow.getDate());
    tomorrow.setHours(0, 0, 0, 0);

    let remainingSeconds = Math.floor((tomorrow - now) / 1000);
    return remainingSeconds > 0 ? remainingSeconds : 0;
}

// 1桁の場合0を付ける関数
function formatTime(time) {
    return time < 10 ? "0" + time : time;
}
              
            
!
999px

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