Implement map()

[julien-f]

iterable::map(mapper, [ opts ]).then((collection) => {
  // Like iterable::all(), collection is an object if iterable
  // was a plain object, a map otherwise.
})

• wait for the iterable promise to be resolved
• execute mapper on an entry ASAP
• support a concurrency option defaulting to Infinity

[perrin4869]

Hm... I noticed that you removed the map from 0.19.0. It was actually quite useful.
Did it have any missing features? Do you plan to return it?

[julien-f]

Hi,

It was removed because I wasn't satisfied with its features and API.

What features were you using that is not available via a simple

await Promise.all(Array.from(iterable, async item => {
 // …
}))

[perrin4869]

Well, I had code that looked like this:

return Promise.all([manager.getAllUserIds(), getUserIds(processId)])
      .then(apply(difference))
      ::map(disconnecter.disconnect(?, 0));

Using @babel/proposal-partial-application and @babel/proposal-function-bind. Without ::map I would be left with something like:

return Promise.all([manager.getAllUserIds(), getUserIds(processId)])
      .then(apply(difference))
      .then(ids => Promise.all(ids.map(disconnecter.disconnect(?, 0))));

Not the end of the world but I really like the syntax with ::map

[julien-f]

I like this syntax as well, unfortunately it looks like it's never gonna be standardized, therefore I'll be moving away from it.

If you want to keep using it, you can use a simple implementation like:

function map(cb) {
  return Promise.all(Array.from(this, cb));
}

[perrin4869]

Well, more recently there has been some progress as far as this proposal goes: https://github.com/tc39/proposal-extensions
Still just in stage 1 though

[julien-f]

Thanks for this info, I'll keep an eye on it 🙂