index.js

const express = require('express');
const users = require('./users');

const app = express();

const authenticate = ({ username, password }) => {
  const foundUser = users.find((user) => {
    return user.username === username
  })
  if (foundUser) {
    if (foundUser.password === password) {
      return foundUser
    }
  }
}

const checkUser = (req, res, next) => {
  const user = authenticate(req.body)
  if (user) {
    req.role = user.role
    next()
  } else {
    return res.status(403).send('not authorized!')
  }
}

app.post('/login', express.json(), checkUser, (req, res) => {
  res.send('successfully accessing this endpoint!')
})

app.listen(5000, () => console.log('app listening on port 5000'))

users.js

const users = [
  {
    username: "harrison",
    password: "password",
    role: "admin"
  },
  {
    username: "anhar",
    password: "password",
    role: "card game expert"
  },
  {
    username: "lav",
    password: "password",
    role: "cricket expert"
  },
  {
    username: "leah",
    password: "password",
    role: "meetups expert"
  }
]

module.exports = users