横並び複数のストップウォッチ

横並び複数ストップウォッチ
仕組み
1. 構造
2. コード

横並び複数ストップウォッチ

00:00:00

仕組み

構造

querySelectorAllとforEach、アロー関数を用いて反復処理をします。

スマートフォンでは解像度の関係上、5つ全て横並びにはなりません。実装する際はCSSを調整してください。

コード

document.querySelectorAll('.stopwatch').forEach(stopwatch => {
let startTime;
let updatedTime;
let difference;
let timerInterval;
let isRunning = false;

const display = stopwatch.querySelector('.display');
const startStopBtn = stopwatch.querySelector('.startStopBtn');
const resetBtn = stopwatch.querySelector('.resetBtn');

function startStopWatch() {
  if (!isRunning) {
    startTime = new Date().getTime() - (difference || 0);
    timerInterval = setInterval(updateDisplay, 1000 / 60);
    startStopBtn.textContent = 'Stop';
    isRunning = true;
  } else {
    clearInterval(timerInterval);
    startStopBtn.textContent = 'Start';
    isRunning = false;
  }
}

function resetWatch() {
  clearInterval(timerInterval);
  isRunning = false;
  startStopBtn.textContent = 'Start';
  difference = 0;
  display.textContent = '00:00:00';
}

function updateDisplay() {
  updatedTime = new Date().getTime();
  difference = updatedTime - startTime;

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

  hours = (hours < 10) ? '0' + hours : hours;
  minutes = (minutes < 10) ? '0' + minutes : minutes;
  seconds = (seconds < 10) ? '0' + seconds : seconds;

  display.textContent = `${hours}:${minutes}:${seconds}`;
}

startStopBtn.addEventListener('click', startStopWatch);
resetBtn.addEventListener('click', resetWatch);
});

<div class="stopwatches">
<div class="stopwatch">
<p>1</p>
<div class="display">00:00:00</div>
<button class="startStopBtn">Start</button><button class="resetBtn">Reset</button></div>
<div class="stopwatch">
<p>2</p>
<div class="display">00:00:00</div>
<button class="startStopBtn">Start</button><button class="resetBtn">Reset</button></div>
<div class="stopwatch">
<p>3</p>
<div class="display">00:00:00</div>
<button class="startStopBtn">Start</button><button class="resetBtn">Reset</button></div>
<div class="stopwatch">
<p>4</p>
<div class="display">00:00:00</div>
<button class="startStopBtn">Start</button><button class="resetBtn">Reset</button></div>
<div class="stopwatch">
<p>5</p>
<div class="display">00:00:00</div>
<button class="startStopBtn">Start</button><button class="resetBtn">Reset</button></div>
</div>
<p><script src="script.js"></script></p>

.stopwatch {
  display:inline-block;
  text-align: center;
  border: 1px solid #000;
  padding: 4px;
  border-radius: 5px;
}

.display {
  font-size: 20px;
  margin-bottom: 10px;
}

button {
  font-size: 12px;
  padding: 5px 10px;
  margin: 5px;
}