last.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #finalpage{
            /* border: 1px solid red; */
            width:400px;
           margin: auto;
           margin-top: 50px;
        }
        #continue{
            background-color: black;
            color: white;
            height:25px;
            padding:5px;
        }
    </style>
</head>
<body>
    <div style="text-align:center"><h2>CHECKOUT</h2></div>
    <div id="finalpage">
        <h2>Your order has successfully placed</h2>
    <h2>Order id = 009865412</h2>
    <button id="continue">CONTINUE SHOPPING</button>
    </div>
    
</body>
</html>
<script>
    document.querySelector("#continue").addEventListener("click",backhome);
    function backhome(){
       window.location.href="index.html";
    }
</script>