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

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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".

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