How to return a promise when an array of functions is passed, to another function as an arguments?

user_8456190 0
Viewed 1547

A question can be found here:

Implement the getInParallel function that should be used to invoke multiple API calls in parallel. The function accepts an array of functions that return a Promise. The function should return a Promise which should resolve to an array of results from the apiCalls argument.

For example, calling the following code should print [ 'First API call!', 'Second API call!' ]:

let promise = getInParallel([() => Promise.resolve("First API call!"),
                         () => Promise.resolve("Second API call!")]);
if(promise) {
  promise.then((result) => console.log(result)).catch((err) => console.log(err));
}

This is my solution:

function getInParallel(apiCalls) {
  // extract function one by one from array
  // then return each function's Promise to 'rFunt' as Promise.all only accepts array, iterable of promises as an input
  let rFunt = apiCalls.map((funct) => {
    return funct()
  })
  return Promise.all(rFunt).then((res) => {
    return res
  })
}

let promise = getInParallel([() => Promise.resolve("First API call!"),
() => Promise.resolve("Second API call!")]);
if (promise) {
  promise.then((result) => console.log(result)).catch((err) => console.log(err));
}
module.exports.getInParallel = getInParallel;

Are there any other ways/concept to solve this?

promise node.js asynchronous javascript
4 Answers

Your answer is pretty straight-forward, and maybe the simplest one.
I will rewrite getInParallel as below (usually we need type checking, omited here)

const parallel = funcs => Promise.all(funcs.map(fn => fn()));
user_50016440

Your solution is pretty close yet needs some modifications. Please check the code below:

function getInParallel(apiCalls) {
  // Write your code here
  let functions = apiCalls.map(apiCall => apiCall());
  return Promise.all(functions).then(response => response);
}

let promise = getInParallel([
  () => Promise.resolve("First API call!"),
  () => Promise.resolve("Second API call!")
]);
if (promise) {
  promise.then((result) => console.log(result)).catch((err) => console.log(err));
}

user_80804480

Here is a clean way to go about it

function getInParallel(apiCalls) {
  // extract function one by one from array
  // then return each function's Promise to 'rFunt' as Promise.all only accepts array, iterable of promises as an input
  let resFunt = apiCalls.map((funct) => {
    return funct()
  })
  return Promise.all(resFunt).then((res) => {
    return res
  })
}

let promise = getInParallel([() => Promise.resolve("First API call!"),
() => Promise.resolve("Second API call!")]);
if (promise) {
  promise.then((result) => console.log(result)).catch((err) => console.log(err));
}
module.exports.getInParallel = getInParallel;

user_95802870

Here is the short way.

function getInParallel(apiCalls) {
  return Promise.all(apiCalls.map(f=>f()));
}

let promise = getInParallel([() => Promise.resolve("First API call!"),
                             () => Promise.resolve("Second API call!")]);
if(promise) {
  promise.then((result) => console.log(result)).catch((err) => console.log(err));
}
module.exports.getInParallel = getInParallel;
user_90140070
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