index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Counter Project</title>
</head>
<body>
    
    <!-- <button onclick="Increment()"> Increment </button>
    <button onclick="Decrement()"> Decrement </button>
    <button onclick="Reset()"> Reset </button> -->

    <button onclick="change()">Change</button>

    <script>

        // var num = document.querySelector('#number');
        // var counter = 0

        // function Increment(){
        //     counter++;
        //     num.innerText = counter;
        // }

        // function Decrement(){
        //     counter--;
        //     num.innerText = counter;
        // }

        // function Reset(){
        //     counter = 0;
        //     num.innerText = counter;
        // }
        
        const colors = ['red', 'blue', 'green', 'pink', 'yellow', 'orange', 'lightblue', 'lightgreen', 'grey'];
        
        function change(){
            const colorIndex = parseInt(Math.random() * colors.length);
            console.log(colorIndex);
            document.body.style.backgroundColor= colors[colorIndex];
        }


    </script>
    
</body>
</html>