How to use

intersectionBy

function

in

lodash

/**
 * Returns mutual users of group members and user
 * @param {Number} user UserID
 * @param {Number} group GroupID
 */
const mutualGroupMembers = async (user, group) => {
 let myFollowings = await db.query(
   'SELECT follow_system.follow_to AS user, follow_system.follow_to_username AS username FROM follow_system WHERE follow_system.follow_by=?',
   [user]
  ),
  grpMembers = await db.query(
   'SELECT group_members.member AS user, users.username AS username FROM group_members, users WHERE group_id = ? AND group_members.member = users.id ORDER BY group_members.joined_group DESC',
   [group]
  ),
  mutuals = intersectionBy(myFollowings, grpMembers, 'user')

 return mutuals
}

/**
 * Returns mutual users
 * Returns mutual users of session & user
 * @param {Number} session Session ID
 * @param {Number} user User ID
 */
const mutualUsers = async (session, user) => {
 let myFollowings = await db.query(
   'SELECT follow_system.follow_id, follow_system.follow_to AS user, follow_system.follow_to_username AS username, users.firstname, users.surname FROM follow_system, users WHERE follow_system.follow_by=? AND follow_system.follow_to = users.id',
   [session]
  ),
  userFollowers = await db.query(
   'SELECT follow_system.follow_id, follow_system.follow_by AS user, follow_system.follow_by_username AS username, users.firstname, users.surname FROM follow_system, users WHERE follow_system.follow_to=? AND follow_system.follow_by = users.id',
   [user]
  ),
  mutuals = intersectionBy(myFollowings, userFollowers, 'user')

 return mutuals
}