pipe & branch async code

index.js

import _ from 'lodash/fp';

const pipe = (...list) =>
    (args) =>
        _.flatten(list).reduce((p, fn) => p.then(fn), Promise.resolve(args))

const branch = (...list) =>
    (args) =>  Promise.all(list.map(fn => fn(args)))


function getUsersByIds([id1, id2]) {
    return [
        {
            id: id1,
        },
        {
            id: id2,
        }
    ];
}

function getUsersFriends(arr) {
    return arr.map((val, index) => ({
        name: 'friend-' + index,
    }));
}

function getUsersN1(arr) {
    return arr.map((val, index) => ({
        name: 'N1-' + index,
    }));
}

function log(arr) {
    console.log(JSON.stringify(arr, null, 2));
}

const identity = data => data;

function getStuffByNames(names) {
    return names.map(name => 'Alex connait ' + name);
}

const selectArg = (argNb) => ([...args]) => args[argNb];

pipe(
    getUsersByIds,
    branch(
        user => user,
        pipe(
            getUsersFriends,
            friends => friends.map(f => f.name),
            getStuffByNames
        ),
        getUsersN1
    ),
    ([user, friends, n1]) => ({
        users: {
            user,
            n1,
            friends,
        }
    }),
    branch(
        identity,
        log
    ),
    selectArg(1)
)([1,2])
.then(res => {
    console.log(res);
})
.catch(err => {
    console.log(err);
})