Export countries to firestore document

index.js

const fetch = require('node-fetch');
const fireAdmin = require('firebase-admin');

fireAdmin.initializeApp({
  credential: fireAdmin.credential.applicationDefault()
});

const getCountries = () =>
  new Promise((resolve, reject) => {
    fetch('https://restcountries.eu/rest/v2/all')
      .then(res => res.json())
      .then(json => {
        resolve(json.map(({ name }) => name));
      });
  });

(async () => {
  const firestore = fireAdmin.firestore();

  const countriesRef = firestore.doc('config/fighters');

  const countries = await getCountries();
  await countriesRef.update({ countries });
})();