Analog to `Rx.Observable.toPromise()` ?

One of the nicest things about most is how well it plays with Promises. However unless I miss something there’s only one way to extract values from the stream to a promise and that’s stream.reduce. Obviously you can achieve everything you need with reduce but it can be hard to read and/or a pain to implement.

A common use case I have is doing some manipulation on a stream so it ends up with only one value using a combination of stream.filter, stream.take, most-buffer etc. and finishing that with an ugly .reduce((_, v) => v) which is not the most readable line.

Rx observables have a toPromise() function that actually resolves to the last event in the stream. I’m not a big fan as it is to really explicit as to which value is taken.

So here the proposal.

stream.retrieveFirst()

which is sugar for

stream.take(1).reduce((_, v) => v)

and

stream.retrieveLast()

which is sugar for

stream.reduce((_, v) => v)

What do you think?

[briancavalier]

Hey @cloderic, thanks for opening the discussion.

For your own usage, you can just wrap these up in functions, and then just call them, or use them with thru.

const retrieveLast = stream => stream.reduce((_, v) => v)

const retrieveFirst = stream => retrieveLast(stream.take(1))

For the larger community, I think this could be a nice mostjs-community package. Is that something you’d be interested in contributing?

Cheers!

[briancavalier]

@cloderic Awesome, and we released most 1.6.0 with the thru return type update.