Proposal: Allow Promise callbacks to be removed

[Naveen Chawla]

How can you terminate an async call? All you're doing is refusing to handle
the result. Explain how I'm wrong if so.

On Tue, 24 Apr 2018 at 13:27 Andrea Giammarchi <andrea.giammarchi at gmail.com>
wrote:

> The `isStillValid` is limited in possibilities. I think listeners open
> new possibilities, specially for very complex operations.
>
> I see a simple scenario like the following one:
>
>    - user asks for a very expensive task clicking section A
>    - while it's waiting for it, user changes idea clicking section B
>    - both section A and section B needs that very expensive async call
>    - drop "going to section A" info and put "go to section B" to that
>    very same promise
>    - whenever resolved, do that action
>
> A caching mechanism to trigger only once such expensive operation would
> also work, yet it's not possible to drop "go into A" and put "go into B"
>
> My PoC also is per promise, so if you use `.then()` over the passed along
> promise, you can add your own listeners in there too, without affecting the
> initial one (and vice versa)
>
>
>
>
> On Mon, Apr 23, 2018 at 11:07 PM, Alex Vincent <ajvincent at gmail.com>
> wrote:
>
>>
>> My proposal is that we add a way of removing a particular callback, or
>>> all callbacks, from a Promise. This is different to cancelling a Promise
>>> and would instead happen if you want the operation to continue but are no
>>> longer interested in running a function when the Promise is resolved or
>>> rejected.
>>>
>>
>> Devil's advocate from the peanut gallery:  what's so hard about adding:
>>
>> ```javascript
>> if (!isStillValid) return;
>> ```
>> --
>> "The first step in confirming there is a bug in someone else's work is
>> confirming there are no bugs in your own."
>> -- Alexander J. Vincent, June 30, 2001
>>
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>>
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