Setting an object on req. in the first of two middlwares seems to not be present at the time the second middlware is called

Question

I have two express middlwares where one is setting an object to the req and the other that follows it uses that object to turn a switch statement.

Here's an illustration:

module.exports = (req, res, next) => {
  if (!req.headers.authorization) {
    return res.status(401).end()
  }
  const token = req.headers.authorization.split(' ')[1]
  return jwt.verify(token, config.database.jwtSecret, (err, decoded) => {
    if (err) { return res.status(401).end() }

    const userId = decoded.sub
    return User.findById(userId, (userErr, user) => {
      if (userErr || !user) {
        return res.status(401).end()
      }
      req.user = {
        _id: user._id,
        name: user.name
      }
      return next()
    })
  })
}

    //My route
        userpage.get('/', authCheck, (req, res) => {
          return Event.findOne()
          .populate('attending.user', 'name') 
          .exec((err, newEvent) => {
            if (err) {
              console.log(err)
              res.status(400).end()
            }
            let uids = []
            let imAttending = false
            newDinner.attending.user.map(obj => {
              uids.push(obj._id)
              })
            console.log(uids) // Shows the array with all uids
            // Double checked that it is indeed an array
            let isArr = Object.prototype.toString.call(uids) === '[object Array]'
            console.log(isArr) // true
            console.log(req.user._id) // Shows the id and it's indeed matching one of the ids in the uids array
            imAttending = uids.indexOf(req.user._id) > -1
            console.log(imAttending)  // false <--- Should be true
            // Test
            let id = '57ec2203ba3e994c7c9d5832' // I litraly copy pasted that from the console.log(req.user._id)
            imAttendingII = uids.indexOf(id) > -1
            console.log(imAttendingII) // true ???? what the heck?
            // checking it's the same type as suggested in one of the comments
            let check = ['57ec2203ba3e994c7c9d5832'].indexOf(req.user._id) === -1
            console.log(check) //true
          })
        })

The comments below reassured me that it's not an async issue and following the results I'm getting I'm lost at what it could be.

Edit: The following works though, and shows true. But checking on the _id felds doesn't work even after doing uids.indexOf(req.user._id.toString()) > -1 on the _id element:

newEvent.attending.user.map(obj => {
      names.push(obj.name)
    })
    imAttending = names.indexOf(req.user.name) > -1 // imAttending = true

Answer 1

Decided to add another answer because of the additional information provided in the question.

It looks like you're using MongoDB and Mongoose (which should be in the tags if I'm right). Given that, a user document's _id property will not be equal to the string form of it, because the representation is actually ObjectID('blahblahblah'), it's not actually a string under the hood. If you console.log() it, it will look like a string because console.log calls toString() under its hood.

So the evaluation you might want to try is:

imAttending = uids.indexOf(req.user._id.toString()) > -1;
console.log(imAttending); // should be true

As a side note, this is also why it's a great reason to use something like node-inspector to set breakpoints and step through your code, rather than relying on console statements to debug. You'll see the actual representation of the various bits, rather than their stringified form.