如何将返回诺言的函数应用于Ramda中的每个列表项

Question

I have a list of names and each needs to do a database fetch from Firebase. The FireStore get function returns a promise.

How do I work that in to Ramda? I've tried ComposeP/pipeP but I need these to work in a loop.

Think I'm missing something obvious as I'm just getting in to functional programming.

Any help or pointers would be appreciated.

Answer 1

It's not quite clear to me what you're looking for, but at first glance I believe you simply need Promise.all . Here is a simple solution that mocks Firebase and composes Promise.all with the Firebase call. After a 1 second delay, it should log the correct values.

 const people = { barney: {name: 'Barney Rubble', id: 1}, betty: {name: 'Betty Rubble', id: 2}, fred: {name: 'Fred Flintstone', id: 3}, wilma: {name: 'Wilma Flintstone', id: 4} } const FakeFirestore = { get: name => new Promise(r => setTimeout(_ => r(people[name]), 1000)) } const getAll = R.compose(Promise.all.bind(Promise), R.map(FakeFirestore.get)) getAll(['betty', 'wilma']).then(R.map(console.log)) 

 <script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.25.0/ramda.js"></script> 

But note that the Ramda calls are not particularly important here. getAll could just as well be written as const getAll = names => Promise.all(names.map(FakeFirestore.get)) .