timer.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Simple Timer</title>
</head>
<body>
    <h1>Simple Timer</h1>
    <div id="timer">0</div>
    <button onclick="start()">Start</button>
    <button onclick="stop()">Stop</button>
    <button onclick="reset()">Reset</button>

    <script>
        let timer = 0;
        let interval;

        function start() {
            if (!interval) {
                interval = setInterval(() => {
                    timer++;
                    document.getElementById('timer').innerText = timer;
                }, 1000);
            }
        }

        function stop() {
            clearInterval(interval);
            interval = null;
        }

        function reset() {
            stop();
            timer = 0;
            document.getElementById('timer').innerText = timer;
        }
    </script>
</body>
</html>