Javascript Ajax is returns undefined when calling a Web Service

Question

I am using JavaScript rather than JQuery to call a web service. But the problem is I keep getting undefined back as a result. I have done some searching for this but all I seem to find is JQuery related post instead of JavaScript related.

I know that the webservice itself gets the right inputs and returns the right output. I have tested it on its own.

function RegisterFunction() { 
//Calling the web method
//<-- Some code -->
        data = Food_Calorie_Calculator.WebService1.Register(name, password, RegisterFunctionSuccessCallback);
}


function RegisterFunctionSuccessCallback(data) {
        document.getElementById("ResultLabel") = data.;
    }

Here is my script manager:

<asp:ScriptManager ID="ScriptManger1" runat="Server">
            <Services> 
                <asp:ServiceReference Path="~/RegisterService.asmx" />
            </Services>  
        </asp:ScriptManager>

Answer 1

remove data. from your code

  document.getElementById("ResultLabel") = data;

Answer 2

The problem is was sintax error.

instead of:

document.getElementById("ResultLabel") = data;

it should have been:

document.getElementById('ResultLabel').innerHTML = data;

Note the ' ' instead of " ", as well as the .innerHTML