gistfile1.md

A+ Promises vs. jQuery.defer

thisPromiseRejects.then(fulfillHandler1)
  .then(fulfillHandler2, rejectHandler2);

###jQuery rejectionHandler1 and rejectionHandler2 will be called.

###A+ rejectionHandler1 and rejectionHandler2 will be called.

thisPromiseRejects.then(fulfillHandler1, rejectHandler1)
  .then(fulfillHandler2, rejectHandler2);

###jQuery rejectionHandler1 and rejectionHandler2 will be called.

###A+ Assuming rejectHandler1 does not throw an error, rejectHandler1 and fulfillHandler2 will be called.

Spec

then must return a promise [3.3].

promise2 = promise1.then(onFulfilled, onRejected);

1. If either onFulfilled or onRejected returns a value x, run the Promise Resolution Procedure [[Resolve]](promise2, x).
2. If either onFulfilled or onRejected throws an exception e, promise2 must be rejected with e as the reason.
3. If onFulfilled is not a function and promise1 is fulfilled, promise2 must be fulfilled with the same value as promise1.
4. If onRejected is not a function and promise1 is rejected, promise2 must be rejected with the same reason as promise1.