should-follow.js

// npm install twit
const Twit = require("twit");

// Fill this in
const T = new Twit({
  consumer_key: "???",
  consumer_secret: "???",
  access_token: "???",
  access_token_secret: "???"
});

const user = "jbenton";

const otherUsers = [
  "laurahazardowen",
  "shansquared",
  "newsbyschmidt",
  "rbilton",
  "ceodonovan",
  "zseward"
];

// Get who each user is following
Promise.all([user, ...otherUsers].map(getAllFollowing)).then(results => {
  const followers = {};

  // Get shared ids that user isn't following, but other people are
  results.slice(1).forEach((ids, i) =>
    ids.forEach(id => {
      if (!results[0].includes(id)) {
        if (!followers[id]) {
          followers[id] = [];
        }
        followers[id].push(otherUsers[i]);
      }
    })
  );

  // Convert IDs back to user details and print the top 100
  getUsernames(followers).then(printResults);
});

// Log the top 100 with name + bio
function printResults(results) {
  results.forEach(({ name, username, description, followers }) =>
    console.log(
      [
        name + "(@" + username + ")",
        "Followed by " + followers.join(", "),
        description
      ]
        .filter(d => d)
        .join("\n") + "\n"
    )
  );
}

function getUsernames(followers) {
  // Pick top 100 by number of shared followers from the list
  const top100 = Object.entries(followers)
    .sort((a, b) => b[1].length - a[1].length)
    .slice(0, 100)
    .map(p => p[0]);

  // Convert ids to user details
  return T.post("users/lookup", {
    user_id: top100.join(","),
    include_entities: false
  }).then(({ data }) =>
    data
      .map(d => ({
        name: d.name,
        username: d.screen_name,
        description: d.description,
        followers: followers[d.id_str]
      }))
      .sort((a, b) => b.followers.length - a.followers.length)
  );
}

// Assumes following 5000 or fewer, no pagination
function getAllFollowing(username) {
  return T.get("friends/ids", {
    screen_name: username,
    stringify_ids: true,
    count: 5000
  }).then(({ data }) => data.ids);
}