JavaScript/counter.html at main · AnshumanSinghh/JavaScript · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Counter</title>
</head>
<body>
    <h1>Counter</h1>
    <h2>Hello!</h2>
    <p>You have clicked this button <b><span id="p">0</span></b> time(s).</p>
    <button onclick="Counter()">Count</button>
    <button>Count 2</button>
</body>
<script>
    //  to define a new variable use let keyword.
    let c = 0;

    function Counter() {
        c += 1;
        // alert(`Counter = ${c}`);
        document.getElementById("p").innerText = c;

        if (c % 2 === 0) {
            document.querySelector('h1').innerHTML = "Goodbye!";
        }
        else{
            document.querySelector('h1').innerHTML = "Welcome!";
        }

        // another way of doing the same thing
        if (document.querySelector('h2').innerHTML === "Hello!") {
            document.querySelector('h2').innerHTML = "Goodbye!";
        }
        else {
            document.querySelector('h2').innerHTML = "Hello!";
        }
    }
    // adding an event listener
    document.querySelectorAll('button')[1].onclick = Counter;
</script>
</html>