Version 1.1.1 / 2014-05-05
These changes help clarify and improve the specification, but should not affect implementation conformance.
- Clarified fulfillment value and rejection reason propagation when
onFulfilledandonRejectedpassed tothenare not functions.
Version 1.1 / 2013-09-29
These changes help clarify and improve the specification, but should not affect implementation conformance.
- Improved the introductory text to give a better idea of what promises are, and what the purpose of Promises/A+ is.
- Separated out the concept of a possibly-nonconformant "thenable" from the concept of a conformant "promise."
- Added a definition for "exception."
These changes impose new requirements on implementations, either to specify a previously-undefined behavior, or to fix something incorrect that the spec allowed in version 1.0.
- Specified that
onFulfilledandonRejectedmust be called as functions, with nothisvalue. - Changed the way in which asynchronicity was mandated for
onFulfilledandonRejected, to enforce the important invariant that the stack be clear. In particular, the new wording prevents fulfilling or rejecting a promise from ever synchronously calling the handlers. - Prohibited implementations from calling
onFulfilledoronRejectedbefore the corresponding promise was respectively fulfilled or rejected. - Specified the Promise Resolution Procedure, instead of leaving the mechanism for adopting a thenable's state unspecified.
- The recursive nature of the now-specified procedure improves upon the naïve non-recursive suggestion given in version 1.0.
- Edge cases, such as how to deal with a getter for
then, or synchronous exceptions that could be thrown during the process, are nailed down. - Self-resolution now causes rejection with a
TypeError. - Infinite recursion from circular thenable chains are discussed, optionally allowing this to result in a
TypeError.
Version 1.0 / 2012-12-06
- Initial release. For differences from its predecessor, the Promises/A specification, see Differences from Promises/A.