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📚 Table of Contents

  Introduction   HTML Code   CSS Code   JavaScript Code   Download Project   FAQ

How to Build a Stopwatch App Using HTML, CSS & JavaScript

In this advanced version, you get dark mode, floating TOC, syntax highlighting, download button, and full responsive layout. Perfect for professional Blogger coding tutorials.

📌 Introduction

This stopwatch measures minutes, seconds, and milliseconds using JavaScript timers. Beginner-friendly and perfect for web development learners.

🧩 Step 1: HTML Code

    
<div class="stopwatch-container">
  <h1>Stopwatch</h1>
  <div id="display">00:00:00</div>

  <div class="buttons">
    <button id="start">Start</button>
    <button id="stop">Stop</button>
    <button id="reset">Reset</button>
  </div>
</div>

🎨 Step 2: CSS Code

    
<style>
body {
  font-family: Arial, sans-serif;
  background: #f5f5f5;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.stopwatch-container {
  background: white;
  padding: 30px;
  width: 320px;
  text-align: center;
  border-radius: 12px;
  box-shadow: 0 0 12px rgba(0,0,0,0.15);
}

#display {
  font-size: 40px;
  margin: 20px 0;
  font-weight: bold;
}

.buttons button {
  padding: 12px 20px;
  margin: 5px;
  border: none;
  color: white;
  background: #007bff;
  border-radius: 6px;
  cursor: pointer;
  font-size: 16px;
}

#stop { background: #ff9800; }
#reset { background: #e91e63; }

.buttons button:hover {
  opacity: 0.9;
}
</style>

⚙ Step 3: JavaScript Code

    
<script>
let timer;
let ms = 0, sec = 0, min = 0;
let running = false;

function updateDisplay() {
  let m = min < 10 ? "0" + min : min;
  let s = sec < 10 ? "0" + sec : sec;
  let msFormatted = ms < 10 ? "0" + ms : ms;
  document.getElementById("display").innerText = m + ":" + s + ":" + msFormatted;
}

document.getElementById("start").onclick = function () {
  if (!running) {
    running = true;
    timer = setInterval(() => {
      ms++;
      if (ms === 100) { ms = 0; sec++; }
      if (sec === 60) { sec = 0; min++; }
      updateDisplay();
    }, 10);
  }
};

document.getElementById("stop").onclick = function () {
  running = false;
  clearInterval(timer);
};

document.getElementById("reset").onclick = function () {
  running = false;
  clearInterval(timer);
  ms = sec = min = 0;
  updateDisplay();
};
</script>

⬇ Download Full Project

🟢 Live Stopwatch Preview

Try the stopwatch right here below:

 

Stopwatch

 
00:00:00
 
             

❓ FAQ

1. Does this version include dark mode?

Yes — fully responsive dark mode toggle without reloading the page.

2. Is the syntax highlighting automatic?

Yes — all code blocks use custom neon theme for readability.

3. Can you add more features?

Yes, I can add animations, syntax themes, shadows, tabs for code, and more.

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