Mastodon scraper to get all of the folks followed by folks that you follow (your second-degree followers). Download your following_accounts.csv and put it in the same folder as this script. DO NOT RUN THIS if you follow lots (1000+) folks!!! That would be rude.

scrape.js

const fs = require('fs');
const readline = require('readline');
const https = require('https');

const reqOptions = {
  timeout: 1000,
};

function get(url) {
  // console.log(url);
  return new Promise((resolve, reject) => {
    const request = https.request(url, reqOptions, (response) => {
      let data = '';

      response.on('data', (chunk) => {
        data = data + chunk.toString();
      });

      response.on('end', () => {
        try {
          const body = JSON.parse(data);
          resolve(body);
        }
        catch(error) {
          reject(error);
        }
      });
    })

    request.on('error', (error) => {
      reject(error);
    });
    request.end();
  });
}

function write(stream, output) {
  let line  = output.join(',') + "\n";
  return stream.write(line);
}

async function run() {
  const inputStream = fs.createReadStream('following_accounts.csv');

  const rl = readline.createInterface({
    input: inputStream,
    crlfDelay: Infinity
  });

  let userList = [];

  for await (const line of rl) {
    let username = line.split(',')[0];
    userList.push(username);
  }

  // Remove headers.
  userList.shift();

  console.log(userList);

  let fileArgs = {};
  let followfollowStream = fs.createWriteStream('followfollows.csv', fileArgs);

  let userdata = {};
  let follows = {};
  for(const username of userList) {
    let [user, service] = username.split('@');

    const lookupUrl = `https://${service}/api/v1/accounts/lookup?acct=@${user}`;

    let info;
    try {
      info = await get(lookupUrl);
    } catch(error) {
      console.log('error', error);
      continue;
    }

    if(info.fields && info.fields.length) {
      info.link1 = info.fields[0];
      info.link2 = info.fields[1];
      info.link3 = info.fields[2];
      info.link4 = info.fields[3];
    }
    delete info.fields;

    console.log('Getting ', info.display_name);

    const followUrl = `https://${service}/api/v1/accounts/${info.id}/following`;

    info.following = [];

    let following;
    try {
      following = await get(followUrl);
      if(!following || typeof following[Symbol.iterator] !== 'function') {
        continue;
      }
    } catch(error) {
      console.log('error', error);
      continue;
    }

    for(const follow of following) {
      let [namePart, serverPart] = follow.acct.split('@');

      if(!serverPart) {
        serverPart = service;
      }

      let temp = {
        'display_name': follow.display_name.replace(',', ' '),
        'acct': follow.acct,
        'url': `https://${serverPart}/@${namePart}`
      };

      // We don't do anything with this data at present.
      // info.following.push(temp);


      if(!follows[follow.acct]) {
        follows[follow.acct] = temp;
        follows[follow.acct].count = 1;
      }
      else {
        follows[follow.acct].count++;
      }
    }
  }

  // Flatten
  follows = Object.values(follows);

  follows.sort((a,b) => {
    return b.count - a.count;
  });

  write(followfollowStream, ['Name', 'Account', 'Url', 'Count']);

  for(const follow of follows) {
    write(followfollowStream, [follow.display_name, follow.acct, follow.url, follow.count]);
  }

  return Promise.resolve();
}

run().then(() => {
  console.log('done.');
});