Question

161

How to return a value from a function that calls $.getJSON?

rated 0 times [ 166] [ 5] / answers: 1 / hits: 40815 / 14 Years ago, wed, november 17, 2010, 12:00:00

function lookupRemote(searchTerm)

{

   var defaultReturnValue = 1010;

   var returnValue = defaultReturnValue;



   $.getJSON(remote, function(data)

   {

      if (data != null)

      {

           $.each(data.items, function(i, item)

           {

               returnValue = item.libraryOfCongressNumber;

           });

      }

    });

    return returnValue;

}

Why is the returnValue from this function alway equal to the default value set at the beginning of the function and never to the value retrieved from the JSON lookup?

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sabrina

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answered 14 Years ago skylerselenem · Accepted Answer

This happens because that callback function (function(data) {...}) runs later when the response comes back...because it's an asynchronous function. Instead use the value once you have it set, like this:

function lookupRemote(searchTerm)

{

    var defaultReturnValue = 1010;

    var returnValue = defaultReturnValue;

    $.getJSON(remote, function(data) {           

        if (data != null) {

              $.each(data.items, function(i, item) {                 

                    returnValue = item.libraryOfCongressNumber;

              });

        }

        OtherFunctionThatUsesTheValue(returnValue);

     });

}

This is the way all asynchronous behavior should be, kick off whatever needs the value once you have it...which is when the server responds with data.