将Promise.all（[promise of list]）转换为ramda

Question

I have written a function which returns a list of promises (code in ramda), and I then have to surround that with Promise.all() to resolve all promises and sends it back to promise chain.

For eg

// Returns Promise.all that contains list of promises. For each endpoint we get the data from a promised fn getData().
const getInfos = curry((endpoints) => Promise.all(
  pipe(
    map(getData())
  )(endpoints))
);

getEndpoints()   //Get the list of endpoints, Returns Promise
  .then(getInfos) //Get Info from all the endpoints
  .then(resp => console.log(JSON.stringify(resp))) //This will contain a list of responses from each endpoint

promiseFn is the function that returns a Promise.

How can I best convert this function into complete Ramda like, and use of either pipeP or something else? Can someone recommend?

Answer 1

Not sure what you want to achieve, but I would rewrite it like that :

const getInfos = promise => promise.then(
  endpoints => Promise.all(
    map(getData(), endpoints)
  )
);

const log = promise => promise.then(forEach(
  resp => console.log(JSON.stringify(resp))
));

const doStuff = pipe(
  getEndpoints,
  getInfos,
  log
);

doStuff();

Answer 2

I think you mean using pointfree notation .

I'd recommend using compose . It's a great tool when using ramda .

const getInfos = R.compose(
  Promise.all,
  R.map(getData),
);

// Now call it like this.
getInfos(endpoints)
  .then(() => console.log('Got info from all endpoints!'));

// Because `getInfos` returns a promise you can use it in your promise chain.
getEndpoints()
  .then(getInfos) // make all API calls
  .then(R.map(JSON.stringify)) // decode all responses
  .then(console.log) // log the resulting array

Answer 3

I'd try something like this:

const getEndpoints = () =>
  Promise.resolve(['1', '2', '3', '4', '5', '6', '7', '8'])
const getEndpointData = (endpoint) =>
  Promise.resolve({ type: 'data', endpoint })

const logEndpointData = pipe(
  getEndpoints,
  then(map(getEndpointData)),
  then(ps => Promise.all(ps)),
  then(console.log)
)

logEndpointDatas()

I hesitate to combine just 2 functions with pipe / compose. Things like then(map(callback)) reads fine once you get used to it. And I try not to take promises as parameters.