09_Async/three.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Set Interval</title>
</head>
<body>
    <h1></h1>
    <button id="start">Start</button>
    <button id="stop">Stop</button>
</body>
<script>
    // Took a variable globally
    let start;

    // Made a func. to update h1's inner text
    function addText(str) {
        document.querySelector('h1').innerHTML += str
    }
    
    // Added a addEventListener in which a setInterval to perform a task on every 1 sec
    document.querySelector('#start').addEventListener('click', function(){
        start = setInterval(addText, 1000, ' Run') // (' Run') parameter passed
    })

    // Added a addEventListener to stop that interval
    document.querySelector('#stop').addEventListener('click', function(){
        clearInterval(start)
    })
</script>
</html>