Callback function inside Deferred objects

Question

I'm trying to follow some javascript lessons where there is an implementation of Deferred. This is the core of the code

getData = function (options) {
  return $.Deferred(function (def) {

    var results = options.results;                    

    getFunction({
      success: function (smt) {                                
        results("test");
        def.resolve(results);
        debugger;
      },
      error: function (response) {                                    
        def.reject();
      }
    }); 

  }).promise();
},

Now the question is.. when i call this function from outside like:

$.when(somthing.getData(options)).
   done(alert(options.results));

debugger;

It happens that FIRSTLY reach the debugger outside the $.when call, and THEN touch the one inside callback SUCCESS function inside the Deferred object...

I don't get it.. shouldn't be the promise done only when def.resolve(results) is reached?...

freakish · Accepted Answer · 2013-03-05 09:22:24Z

1

Everything's correct except for the last line:

$.when(somthing.getData(options)).done(alert(options.results));
debugger;

You call alert ( and debugger ) immediatly here. What you want is to pass a callback to done like this:

$.when(somthing.getData(options))
.done(function(){
    alert(options.results);
    debugger;
});

answered Mar 5, 2013 at 9:22

freakish

57k12 gold badges141 silver badges181 bronze badges

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

2 Comments

Ivan_nn2 Over a year ago

Thank freakish.. that worked like a charm.. Can i ask you why?.. I thought that the function inside DONE was already a callback function... why do i have to define a function like that to call my function?...

freakish Over a year ago

.done accepts a function. What you passed to .done is not a function, but a result of calling alert() ( note the order: first alert is called, then it's result is passed to .done ) which is undefined ( that's what alert returns ). It's like doing .done("test"). What does it mean? What JavaScript is supposed to do with a string? You want to pass a function to .done, so JavaScript will know: "oh, I've received a function, I can call it once when is done".

Collectives™ on Stack Overflow

Callback function inside Deferred objects

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related