functional js async loops

asyncLoops.js

function loadUsers(userIds, load, done) {
    var users = []
    var count = 0

    userIds.forEach(function (id) {
        load(id, function (user) {
            users[userIds.indexOf(user.id)] = user
            count++
            //can not use users.length here
            if (count == userIds.length) {
                done(users)
            }
        })
    })
}

module.exports = loadUsers

officialsolution.js

  function loadUsers(userIds, load, done) {
    var completed = 0
    var users = []
    userIds.forEach(function(id, index) {
      load(id, function(user) {
        users[index] = user
        if (++completed === userIds.length) return done(users)
      })
    })
  }

  module.exports = loadUsers

forEach gives us the index