register

@app.route("/register", methods=["GET", "POST"])
def register():
    """Register user"""

    # User reached route via POST (as by submitting a form via POST)
    if request.method == "POST":

        # Ensure username was submitted
        if not request.form.get("username"):
            return apology("must provide username")

        # Ensure password was submitted
        elif not request.form.get("password"):
            return apology("must provide password")

        # Ensure password matches
        elif request.form.get("password") != request.form.get("confirmation"):
            return apology("password must match")

        else:
            # Hash password
            hash = generate_password_hash(request.form.get("password"))

            # Add user to database
            result = db.execute("INSERT INTO users (username, hash) VALUES(:username, :hash)",
                                username=request.form.get("username"), hash=hash)

            if not result:
                return apology("username already exists...!",)
            else:
                # Remember user
                session["user_id"] = result

                # Flask - flash message
                flash("You are now registered!")

                # Redirect user to home page
                return redirect("/")

    # User reached route via GET (as by clicking a link or via redirect)
    else:
        return render_template("register.html")


{% extends "layout.html" %}

{% block title %}
    Register
{% endblock %}

{% block main %}

    <form id="myForm" action="/register" method="post">
        <div class="form-group">
            <input autocomplete="off" autofocus class="form-control" id="username" name="username" placeholder="Username" type="text">
        </div>
        <div class="form-group">
            <input class="form-control" name="password" placeholder="Password" type="password">
        </div>
        <div class="form-group">
            <input class="form-control" name="confirmation" placeholder="Password (again)" type="password">
        </div>
        <button class="btn btn-primary" type="button">Register</button>
    </form>


    <script>

        $('document').ready(function () {
            $('#myForm').submit(function (event) {
                var username = document.getElementById('username').value;
                event.preventDefault();
                $.get("/check?username=" + username, function (data) {
                    if (!data) {
                        alert("username already taken!");
                        return false;
                    }
                    else {
                        document.getElementById("#myForm").submit();
                        return true;
                    }
                });
            });
        });

    </script>

{% endblock %}