Cancelable promises proposal

Logan Smyth loganfsmyth at
Wed Aug 5 02:51:21 UTC 2015

Glen, sorry if this has been covered in other discussions, but it's not
clear to me so I wanted to ask. Are there some example use-cases where
being able to `.ignore` is preferable to having the promise reject? Promise
chains are about defining flows of data and I can't really see a case where
you'd want to disconnect a promise handler without informing promises
farther down the chain, like your `.then(log)` in your example. To me
anyway, the proposed `.ignore` seems like it adds boat-loads of complexity
with unclear goals.

Also to your question about adding multiple handlers, if that handler has
side-effects, then it would definitely cause bugs if the same promise were
returned for multiple calls to `.then` with the same callback.

On Tue, Aug 4, 2015 at 5:32 PM, Glen Huang <curvedmark at> wrote:

> On Aug 4, 2015, at 1:32 PM, Andrea Giammarchi <andrea.giammarchi at>
> wrote:
> only promises that has passed through their initialization the callback
> would be cancelable,and this could be reflected through a `.cancelable`
> property
> That's precisely the problem. When you made a mistake and thought a
> function should have the ability to abort, you wouldn't reflect
> that `.cancelable` property, you would simply call abort(). Passing a
> different object makes this less likely to happen since it's not thenable.
> and pragmatists would never find out what should be the behavior once
> aborted 'cause Promise can only reject and never be ignored.
> What do you think of the ignore() method I proposed?
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