Question

When I alert the returned value from the jsonServerResponse function, its value is undefined – despite JSON being returned from the process.php page.

function jsonServerResponse(operation, JSOoptionalData) {
        JSOoptionalData = (typeof JSOoptionalData == "undefined") ? 'defaultValue' : JSOoptionalData
        var jqxhr = $.ajax({
            type: "POST",
            url: "process.php",
            data: "apicommand=" + JSOoptionalData,
            success: function (json) {
                return jQuery.parseJSON(json);
            }
        });
}

alert("Response as JS Object: "+jsonServerResponse("operation"));

I know that the problem is that the alert function made before the asynchronous request is complete, but I am unsure how to fix this problem. Any advice is really appreciated 🙂

Answer 1

Ok, I figured it out from a different post. The result can either be handled within the success callback, or you can add an argument that is itself a callback function and apply the result of the ajax request to the callback.

function jsonServerResponse(operation, callback, JSOoptionalData) {
        JSOoptionalData = (typeof JSOoptionalData == "undefined") ? 'defaultValue' : JSOoptionalData
        jqxhr = $.ajax({
            type: "POST",
            contentType: "application/json",
            url: "process.php",
            data: "apicommand=" + operation + "&optionaldata" + JSON.stringify(JSOoptionalData),
            dataType: "json",
            success: function (json) {
                if(typeof callback === 'function') callback.apply(this, [json]);
            }
        });
}


jsonServerResponse("get_something_from_server", function(returnedJSO){
     console.log(returnedJSO.Result.Some_data);
}, "optional_data");

And gdoron, the line you have asked about makes the third argument optional. I hear it’s good practice, if you are going to pass some data onto the server (but you dont know how many variables) to add an optional argument and just pass a js object, convert this to a JSON string, and decode it server-side.

Peace! 🙂