getJSON and variable scope in javascript

Question

In order to make function calls to our back-end php code we've implemented something called an ActionProxy like this:

function ActionProxy(action, input, callback){  
    $.post("ActionProxy.php?method="+action, 
        { data: input},   
            function(data, textStatus, XMLHttpRequest){
                        //return data.ResponseWhatever
                        }
});

The problem we're having is that using data outside the ActionProxy is impossible due to variable scope limitations (we assume), setting
var res = data.ResponseWhatever
or
return data.ResponseWhatever

is pretty futile. How would one handle these responses most appropriately so that functions calling the actionproxy can access the response values?

Alxandr · Accepted Answer · 2010-06-02 18:30:12Z

1

You could use window.ResponseWhatever = data.ResponseWhatever, however, this is not the smartest thing to do. What you want is to do something like this:

function ActionProxy(action, input, callback){
    $.post("ActionProxy.php?method="+action, {data:input},
        function(data, textStatus, xhr){callback(data);});
}

Note: I'm no jQuery-guru, so I might have gotten some of the jQuery-parts wrongly, but the point is that where you want to call return data you instead call callback(data);.

answered Jun 2, 2010 at 18:30

Alxandr

12.5k10 gold badges63 silver badges95 bronze badges

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

2 Comments

nillls Over a year ago

We actually thought of that as well, but given we don't always want a callback we would sometimes like to just receive the return value. Is it at all possible, or is this the way one "is supposed" to write it?

Sean Kinsey Over a year ago

You cannot use return as long as the call is asynchronous, and you really don't want to do a synchronous request due to it being a blocking operation (in many browsers even the UI freeze).

nillls · Accepted Answer · 2010-06-02 20:19:19Z

0

Well, I did sorta the solution provided by Alxandr. It turns out if I want the result, I'll have to implement a callback, but in order to not care about the result I just call the ActionProxy with the first two arguments and check if the callback function is present like so:
function ActionProxy(action, input, callback){



$.post("ActionProxy.php?method="+action, {data:input},
        function(data, textStatus, xhr){

            if(callback){

callback(data);
}

});

}

I would've expected an error calling a three-argument function with two arguments. Oh well - javascript is a strange language. :)

answered Jun 2, 2010 at 20:19

nillls

6234 silver badges11 bronze badges

Collectives™ on Stack Overflow

getJSON and variable scope in javascript

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related