Execute promises sequentially (one at at a time) and return array with the results

promise_map.js

function promiseMap(inputValues, mapper) {
  const reducer = (acc$, inputValue) =>
    acc$.then(acc => mapper(inputValue).then(result => acc.push(result) && acc));
  return inputValues.reduce(reducer, Promise.resolve([]));
}

/* Example */

const axios = require('axios');

function countryFromIp(ip) {
  return axios.get(`http://ip-api.com/json/${ip}`)
    .then(res => res.data.country);
}

promiseMap(["8.8.8.8", "41.182.194.0", "5.34.159.1"], countryFromIp).then(console.log);