index.js

const express = require('express')

const server = express()

server.use(express.json())

const users = []

server.use((req, res, next) => {
  console.time('Request')
  console.log(`Method: ${req.method}; Url: ${req.url}`)

  next()

  console.timeEnd('Request')
})

function checkNameExists(req, res, next) {
  if (!req.body.name) {
    return res.status(400).json({ error: 'User name is required' })
  }

  return next()
}

function checkUserInArray(req, res, next) {
  const user = users[req.params.index]

  if (!user) {
    return res.status(400).json({ error: 'User does not exists' })
  }

  req.user = user;

  return next()
}

server.get('/users', (req, res) => {
  return res.json(users)
})

server.get('/users/:index', checkUserInArray, (req, res) => {
  const { user } = req

  return res.json(user)
})

server.post('/users', checkNameExists, (req, res) => {
  const { name } = req.body

  users.push(name)

  return res.json(users)
})

server.put('/users/:index', checkUserInArray, checkNameExists, (req, res) => {
  const { index } = req.params
  const { name } = req.body

  users[index] = name

  return res.json(users)
})

server.delete('/users/:index', checkUserInArray, (req, res) => {
  const { index } = req.params

  users.splice(index, 1)

  return res.send()
})

server.listen(3000)