html function always return undefined from another js file

Question

First of all I am not using node.js.
My website environment is purely Tomcat + SQL Server + HTML/JSP pages. Secondly I have checked the similar posts and found none of them answers to my question.

Here is what I want to do:

1. Write a js file to modulize an authorization check if a certain user is entitled to view a certain webpage.
2. There are two parameters to pass into the function: username & webpage name.
3. So in each single webpage I could do the authorization check when it's needed.

P.S. when constructing the js function, I've tried several ways incl. factory/prototype/dynamic/parasitic. I believe it's due to my limited programming knowledge, I could not get the desired returned value from the server.

Here below is my case:
In my js file (sisAuthorization.js), it looks like the following:

//-------------------my sisAuthorization.js file Starts here---------------------
// callback example
var clientData = {
    myResult: "not set",
    serverAuthCheck: function(username, webpage){
        $.ajax({
            method: "POST",
            async: false,
            url: "/psd/webpageAuthorization.ajlog",
            dataType: 'json',
            data: {
                "username": username,
                "webpage": webpage
            }, success: function (data) {
                console.log("server answer is " + data.isauthorized);
                if(data.isauthorized == "yes"){
                    this.myResult = "yes";
                    console.log("client answer is " + this.myResult);
                }else{
                    this.myResult = "no";
                }
            }
        });     
    }
}

function getLocalInput(username, webpage, callback, callbackObj){
    callback.apply(callbackObj,[username, webpage]);
}
//-------------------my sisAuthorization.js file Ends here---------------------

In my html/jsp webpage, inside the script block, I write the following:

<!-------------------my Webpage Starts here--------------------->
<script type="text/javascript">

    $(document).ready(function(){
        if(!isUndefined(getCookie("kgusername"))){
            $("#myUsername").html(getCookie("kgusername"));
        }

        //**getCookie("kgusername") returns username**
        //**"updatewbs.jsp" is webpage name**
        getLocalInput (getCookie("kgusername"),"updatewbs.jsp", clientData.serverAuthCheck, clientData);
        console.log (clientData.myResult); // **not set**(I'm expecting "yes" here)

    });

</script>   
<!-------------------my Webpage Ends here--------------------->

Finally in Chrome Console I've got the following:

• sisAuthorization.js:23 server answer is yes
• sisAuthorization.js:26 client answer is yes
• updatewbs.jsp: not set (I'm expecting "yes" here)

Can anyone help???