<form action="https://common-api.timecut.se/api/common/user/loginandredirect" method="post">
    <div>
        <label>Username</label>
        <input name="Username" />
    </div>
    <div>
        <label>Password</label>
        <input name="Password" />
    </div>
    <div>
        <input type="submit" value="Login" />
    </div>
</form>

<div>
    <label>Username</label>
    <input id="username" name="Username" />
</div>
<div>
    <label>Password</label>
    <input id="password" name="Password" />
</div>
<div>
    <input id="login" type="submit" value="Login" />
</div>
<script>
    $("#login").click(
        function () {
            var username = $("#username").val();
            var password = $("#password").val();
            $.ajax("https://common-api.timecut.se/api/common/user/loginbycredential",
                {
                    contentType: "application/json",
                    dataType: "json",
                    method: "POST",
                    data: JSON.stringify({ Username: username, Password: password }),
                    success: function (response) {
                        if (response.Success)
                            window.location.href = response.RedirectUrl;
                        else
                            alert("Login failed (" + response.FailingCode + ")");
                    }
                }
            );
        }
    );
</script>