XEngine

Some things that are "better" with this BetterPromise implementation:

• BetterPromise # unthen(..) / BetterPromise # uncatch(..) / BetterPromise # unfinally(..) allows you to unregister a fulfillment or rejection handler that you previously registered on a promise via then(..) or catch(..), or unregister a resolution handler that you previously registered on a promise via finally(..).

  NOTE: This seems to be the majority use-case for why many like/want "promise cancelation" -- IOW, often what you want is to just stop observing a promise's resolution, not actually forcibly cancel the operation is comes from.

  var p = new BetterPromise(function(res){
     setTimeout(function(){ res(42); },100);
  });

XEngine

Some things that are "better" with this BetterPromise implementation:

• BetterPromise # unthen(..) / BetterPromise # uncatch(..) / BetterPromise # unfinally(..) allows you to unregister a fulfillment or rejection handler that you previously registered on a promise via then(..) or catch(..), or unregister a resolution handler that you previously registered on a promise via finally(..).

  NOTE: This seems to be the majority use-case for why many like/want "promise cancelation" -- IOW, often what you want is to just stop observing a promise's resolution, not actually forcibly cancel the operation is comes from.

  var p = new BetterPromise(function(res){
     setTimeout(function(){ res(42); },100);
  });