compactJoin

[Undistraction]

Is your feature request related to a problem? Please describe.
Returns a string made by inserting the separator between each element and concatenating all the elements into a single string. Before the concatenation happens, the values as compacted using using RA.compact.

Describe the solution you'd like

RA.compactJoin(', ' ['a', '', 'b', null, 'c', undefined, 'd']); //=> 'a, b, c, d'

Describe alternatives you've considered

ad-hoc composition

Additional context
Original issue description:
join currently joins all values, even if undefined (or NaN, or null). How about a safe version that rejects undefined values before joining? Perhaps it could follow the same blacklist as compact, or could allow the blacklist to be configured.

const joinWithComma = join(',')
joinWithComma([1, undefined,]) // '1,'

const safeJoin = s => compose(join(s), reject(isUndefined))
const safeJoinWithComma = safeJoin(',')
safeJoinWithComma([1, undefined, 2]) // '1,2'

REPL

[char0n]

We have already discussed about safe* functions with @guillaumearm in #38 (comment). I think these kind of functions may hide nasty errors because items from the array are implicitly lost before transformation. But safe doesn't tell us anything about this filtering. I can imagine having compactJoin, but would have to see more real world usecases and support for this. For more than 5 years I don't remember having to need something like this, because before I return from function I compact the result of the function and then pass it to higher levels of the app where join can transform them to string.

[Undistraction]

I would argue that is is just a way of being defensive if you don't entirely trust the values you want to joint, but I agree compactJoin is a better name. I'll leave open for now and try and dig up a usecase that will convince you.

[guillaumearm]

Personally, I often write a compactJoin function for making my webpack or rollup configuration like this :

const configuration = {
  ...,
  plugins: compactJoin([
    isProduction ? uglifyPlugin : undefined,
    ...,
  ])
  ...,
}

I use it to conditionally concat things.
IMHO, this is definitively a feature.