ドットインストール - 3分動画でマスターできるプログラミング学習サービス

main.js

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'use strict';
{
    const timer = document.getElementById('timer');
    const start = document.getElementById('start');
    const stop = document.getElementById('stop');
    const reset = document.getElementById('reset');
    let startTime;
    function countUp(){
        // console.log(Date.now() - startTime);
        const d = new Date(Date.now() - startTime);
        const m = String(d.getMinutes()).padStart(2, '0');
        const s = String(d.getSeconds()).padStart(2, '0');
        const ms = String(d.getMilliseconds()).padStart(3, '0');
        timer.textContent = `${m}:${s}.${ms}`;
        console.log(`${m}:${s}.${ms}`);
        setTimeout(() =>{
            countUp();
        }, 10);
    }
    start.addEventListener('click', () =>{
        startTime = Date.now();
        countUp();
    });
}
 
 
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