Superlogin util to update databases according to configuration

updateDBs.js

const SuperLogin = require('superlogin');
const superloginConfig = require('../superlogin.config.js');
const DBAuth = require('superlogin/lib/dbauth');

const superlogin = new SuperLogin(superloginConfig);
const { config, userDB } = superlogin;
const dbAuth = new DBAuth(config);

if (!config.getItem('userDBs.defaultDBs')) {
  console.log('no userDBs.defaultDBs defined');
  process.exit(1);
}

// retrieve all databases configs
let allDBs = [];
function addDBs(dbs, type) {
  if (!Array.isArray(dbs)) return;
  dbs.forEach(dbName => {
    const dbConfig = dbAuth.getDBConfig(dbName);
    dbConfig.type = type; // override type
    allDBs.push(dbConfig);
  });
}
addDBs(config.getItem('userDBs.defaultDBs.private'), 'private');
addDBs(config.getItem('userDBs.defaultDBs.shared'), 'shared');

function getAllUserDocs() {
  return userDB.allDocs({ include_docs: true })
  .then(({ rows }) => (
    rows
      .filter(({ id }) => id !== '_design/auth')
      .map(row => row.doc)
  ));
}

function updateDB(userDoc, dbConfig) {
  console.log('dbConfig: ', dbConfig);
  const { name, designDocs, type, permissions, adminRoles, memberRoles } = dbConfig;
  // Add user db:
  //   get actual db name (depends on private / shared)
  //   create db's when needed
  //   update design docs
  //   get current sessions from userDoc
  //     Update _security doc of db with updated session with new permissions
  return dbAuth.addUserDB(
    userDoc,
    name,
    designDocs,
    type,
    permissions,
    adminRoles,
    memberRoles
  );
}

// get user docs
getAllUserDocs()
.then(userDocs => {
  const userUpdates = [];
  // go through users
  return asyncIterator(userDocs, userDoc => {
    // go through databases
    return asyncIterator(allDBs, dbConfig => {
      // update database
      return updateDB(userDoc, dbConfig)
      .then(finalDBName => {
        // update userDoc's personalDBs
        userDoc.personalDBs[finalDBName] = {
          name: dbConfig.name,
          type: dbConfig.type
        };
        userUpdates.push(userDoc);
      });
    });
  })
  // Bulk save user doc updates
  .then(() => userDB.bulkDocs(userUpdates));
})
.then(() => process.exit());

function asyncIterator(args, callback) {
  return new Promise((resolve, reject) => {
    const results = [];
    if (args.length === 0) resolve(results);
    const clone = [...args];
    function loop(arg) {
      callback(arg).then(function (result) {
        results.push(result);
        if (clone.length > 0) {
          loop(clone.shift());
        } else {
          resolve(results);
        }
      });
    }
    loop(clone.shift());
  });
}