FunctionExample.html

<html>
<head>
    <title>Function Example JavaScript</title>
        <script>
            function displayMessage() { //user-defined function
                alert("This is an alert box sample"); //built-in function
            }
        </script>
</head>
<body>
    <p>Function Example</p>
    <form>
        <input type="button" value="Click me" onClick="displayMessage()" />
    </form>
</body>

</html>