How I would write the promise chain from https://gist.github.com/anonymous/97108e545cb800025b33

gistfile1.js

function getUsernamePromise(input) {
    if (isNumber(input)) {
        return getUserNameById(input);
    }
    if (isString(input)) {
        return getUsernameByEmail(input);
    }
    if (isObject(input)) {
        return Account.find().where(input).exec()
    }
}

function authenticate(input) {
   return getUsernamePromise(input)
   .then(function (username) {
     return getUser(username);
   })
   // chained because we will not need the user name in the next event
   .then(function (user) {
     return getPassword()
     // nested because we need both user and password next
     .then(function (password) {
        if (user.passwordHash !== hash(password)) {
            throw new Error("Can't authenticate");
        }
     });
   });
}