Why are Q.js promises asynchronous after they have been resolved?

Question

If I have the following :

var deferred = Q.defer();

deferred.resolve();

var a = deferred.promise.then(function() {
    console.log(1);    
});

console.log(2); 

...why do I see 2, then 1 in the console?

I understand this output is correct according to the Promises spec, which says to call the function on the next tick (e.g. setTimeout()), even if it is already resolved, but I don't understand why.

I would like to have code that calls then on a series of promises synchronously, assuming that all the promises have been resolved.

My real use case is that I am trying to use Angular's implementation, $q, and I want all of the then callbacks to execute in the same $digest cycle, so that I don't get unnecessary subsequent $digest cycles.

Answer 1

Answer is consistency.

In real code, you don't have promises that are always immediately resolved when created, they would be pointless. So you have promises that sometimes may be immediately resolved.

In that case, you don't want to have a different flow. You want always the same, predictable flow. So you want the next function to be always called on next tick.

Don't use a promise when you don't need one.