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Can I rely on the synchronous nature of allowed pending jquery objects

Please note: This question was about why the jQuery promises implementation does not meet the Promises / A + specification with respect to 2.2.4 .

I noticed that after resolving the pending jQuery object, new calls done will have any calls made that are called synchronously.

var d = $.Deferred(); d.resolve("Foo Bar!"); var fooBar = "Waiting"; d.done(function(data){fooBar = data; }); console.log(fooBar);//Will output "Foo Bar!" because the doneCallback is called synchronously

I expected callbacks to be placed in the event queue (in this case, the output to the console would be “Waiting”) to match the behavior of the call made before the deferred object is resolved. Is my expectation unfounded?

It seems I could not find any documentation on this behavior, so I'm not sure if this is a behavior I can rely on.

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2 answers

This behavior is explicitly described here: http://api.jquery.com/jquery.deferred/

Once an object has entered an allowed or rejected state, it remains in that state. Callbacks can be added to allowed or rejected Deferred - they will be executed immediately.

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I think the problem you should worry about is the "area". This suggests that I understand your question here. You are curious why the “Wait” is not set, because it seems to come after your decision.

For example, you have this snippet here:

  var d = $.Deferred(); d.resolve("Foo Bar!"); var fooBar = "Waiting"; d.done(function(data){fooBar = data; }); console.log(fooBar)

What does it give?

Now we have this:

  var d = $.Deferred(); var fooBar = "Waiting"; d.done(function(data){fooBar = data; }); console.log(fooBar) d.resolve("Foo Bar!");

and this:

  var d = $.Deferred(); d.done(function(data){fooBar = data; }); d.resolve("Foo Bar!"); var fooBar = "Waiting"; console.log(fooBar)

Now check it out!

 var d = $.Deferred(); console.log( fooBar); d.resolve("Foo Bar!"); var fooBar = "Waiting"; console.log( fooBar); d.done(function(data){fooBar = data; }); console.log(fooBar)

Think about the climb and the area .

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