Untitled

<!DOCTYPE html>
<html>
    <head>
        <title>Page Title</title>
        <script src="//code.jquery.com/jquery-1.11.3.min.js"></script>

    </head>

    <body>
        <h1>Register</h1>
        <input id="un" placeholder="username">
        <input id="pw" placeholder="password"><button id="reg">Register</button>
        <button id="login">Login</button>
        <p id="message"></p>
        <script>
        var usernames = ['kevin','balboa','ScriptEd'];
        var passwords = ['dou', '12345','hunter2'];

        $("#reg").click(function() {
            var user = $("#un").val();
            var pass = $("#pw").val();
            if (user === "") {
                $("#message").html("Please fill in a username");
            } else if (pass === "") {
                $("#message").html("Please fill in a password");
            } else {
                if (usernames.includes(user)) {
                    $("#message").html("Username already taken");
                } else {
                    usernames.push(user);
                    passwords.push(pass);
                    $("#message").html("Registered " + user);

                }
            }
        });

        $("#login").click(function() {
            var user = $("#un").val();
            var pass = $("#pw").val();
            if (user === "") {
                $("#message").html("Please fill in a username");
            } else if (pass === "") {
                $("#message").html("Please fill in a password");
            } else {
                if (usernames.includes(user)) {
                    for (var i=0; i<usernames.length; i++) {
                        if (usernames[i] === user) {
                            if (passwords[i] === pass) {
                                $("#message").html("Logged in!");
                            } else {
                                $("#message").html("Wrong Password!");
                            }
                        }
                    }

                } else {
                    $("#message").text(user + " does not exist");
                }
            }
        });
        </script>
    </body>
</html>