$.post("https://myURL.aspx",
            {

                ServerAction: action2,
                username: document.getElementById('username').value,
                password: document.getElementById('password').value,
                txtFName: document.getElementById('txtFName').value,
                txtLName: document.getElementById('txtLName').value,
                /* a lot of other key-value pairs here */
            },
            function(data, status) {

                console.log(status);
                console.log(data);
            }