Javascript function in asp.net

Question

Ok, having an issue withe the return value of a function always returning "undefined"

Heres my code:

//called here:
var res = comms(GENSET_SN);

//the function
function comms(genserial) {
     var Result; 
     //Webservice called here
     MyServices.getCommsState(genserial, "S1", OnComplete1);

     function OnComplete1(args) {
          var Res = eval("(" + args + ")");

          if (Res == 1) {
               Result = 1;
          } else {
                Result = 0;
          }
      }
      return Result;
}

please help!!

Richard Dalton · Accepted Answer · 2012-01-26 15:12:26Z

1

I'm guessing MyServices.getCommsState(genserial, "S1", OnComplete1); is an ajax request?

If so, the value of Result will be returned before it is actually set in the OnComplete1 callback, hence undefined.

You will need to pass in a callback function containing the code that will use the Result value.

You can change the code to do this instead, note that you pass in the function to comms and then call it in OnComplete1:

comms(GENSET_SN, function(res) {
    // do whatever you need with res here!
});

//the function
function comms(genserial, callback) {
     //Webservice called here
     MyServices.getCommsState(genserial, "S1", function(args) {
         var Res = eval("(" + args + ")"); // I would change this aswell, dont use eval!
         callback(Res == 1 ? 1 : 0);
     });            
}

edited Jan 26, 2012 at 15:12

answered Jan 26, 2012 at 14:57

Richard Dalton

35.8k6 gold badges75 silver badges92 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

neilrudds Over a year ago

Yes you are correct it is an AJAX request, how would I go about the callback function? Please excuse me ignorance im only a beginner with javascript.

musefan · Accepted Answer · 2012-01-26 14:56:46Z

1

Simple. You are not defining the value of Result before the function is returned. I assum getCommsState is an async function. If you need this "wrapper" function (comms) I would suggest adding a callback parameter for this too.

answered Jan 26, 2012 at 14:56

musefan

48.5k21 gold badges144 silver badges193 bronze badges

Comments

Joe · Accepted Answer · 2012-01-26 14:57:14Z

JavaScript is Asynchronous

                function OnComplete1(args) {

                    var Res = eval("(" + args + ")");

                    if (Res == 1) {
                        Result = 1;
                    }
                    else {
                        Result = 0;
                    }
                }
                return Result;

needs to be

              function OnComplete1(args) {

                    var Res = eval("(" + args + ")");

                    if (Res == 1) {
                        Result = 1;
                    }
                    else {
                        Result = 0;
                    }

                    // RIGHT NOW - do something with result
               }

Notes:

1 ) eval just isn't good. Modern browsers have JSON already defined or json2.js is widely available

2 ) You might have caught this error if you formatted you code better:

function OnComplete1(args) {
    var Res = JSON.parse(args);

    if (Res == 1) {
        Result = 1;
    }
    else {
        Result = 0;
    }
}
return Result;

Collectives™ on Stack Overflow

Javascript function in asp.net

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related