Allows us to retrieve the diff of users we're following and the one follows us.

instagram-users-diff.js

var request = require('request-promise');
var Q = require('q');
var _ = require('lodash');

var ACCESS_TOKEN = {
  PRIMARY: 'YOU_ACCESS_TOKEN'
};
var SELF_FOLLOWS_API_ENDPOINT = 'https://api.instagram.com/v1/users/self/follows?access_token={token}';
var FOLLOWED_BY_API_ENDPOINT = 'https://api.instagram.com/v1/users/self/followed-by?access_token={token}';
var promises = [];

var collectUsers = function(response) {
  var deferred = Q.defer();
  var users = [];

  var remoteUserIterator = function(response) {
    var parsedResponse = JSON.parse(response);

    for (var i = 0; i < parsedResponse.data.length; i++) {
      users.push(parsedResponse.data[i]);
    }

    if (parsedResponse.pagination.next_url != null) {
      request(parsedResponse.pagination.next_url).then(function(data) {
        remoteUserIterator(data);
      });
    } else {
      deferred.resolve(users);
    }
  };

  remoteUserIterator(response);

  return deferred.promise;
};

var getUsersDiff = function (firstList, secondList) {
  var list = {};

  _.each(firstList, function (item) {
    list[item.id] = item;
  });

  _.each(secondList, function (item) {
    delete list[item.id];
  });

  return _.values(list);
};

var remoteCallDecorator = function (callback) {
  return function (data) {
    var deferred = Q.defer();
    callback(data, deferred);
    return deferred.promise;
  };
};

_.each([SELF_FOLLOWS_API_ENDPOINT, FOLLOWED_BY_API_ENDPOINT], function(url) {
  promises.push(request(url.replace('{token}', ACCESS_TOKEN.PRIMARY)).then(remoteCallDecorator(function(data, deferred) {
    collectUsers(data).then(function(users) {
      deferred.resolve(users);
    });
  })));
});

Q.all(promises).then(function(usersList) {
  console.log(_.map(getUsersDiff(usersList[0], usersList[1]), function(user) { return user.username; }));
});