index.js

const express = require('express')
const cors = require('cors')
const app = express()

app.use(cors())
app.use(express.json())
app.use(express.static('dist'))

let notes = [
  {
    id: 1,
    content: "HTML is easy",
    important: true
  },
  {
    id: 2,
    content: "Browser can execute only JavaScript",
    important: false
  },
  {
    id: 3,
    content: "GET and POST are the most important methods of HTTP protocol",
    important: true
  }
]

app.get('/', (request, response) => {
  response.send('<h1>Hello World!</h1>')
})

/**
 * All notes
 */
app.get('/api/notes', (request, response) => {
  response.json(notes)
})

/**
 * Get note
 */
app.get('/api/notes/:id', (request, response) => {
  const id = Number(request.params.id)
  const note = notes.find(note => note.id === id)

  if (note) {
    response.json(note)
  } else {
    response.status(404).end()
  }
})

/**
 * New note
 */
app.post('/api/notes', (request, response) => {
  const body = request.body

  if (!body.content) {
    return response.status(400).json({
      error: 'content missing'
    })
  }

  const note = {
    content: body.content,
    important: Boolean(body.important) || false,
    id: generateId(),
  }

  notes = notes.concat(note)

  response.json(note)
})

/**
 * Delete note
 */
app.delete('/api/notes/:id', (request, response) => {
  const id = Number(request.params.id)
  notes = notes.filter(note => note.id !== id)

  response.status(204).end()
})

const PORT = process.env.PORT || 3001

app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`)
})

const generateId = () => {
  const maxId = notes.length > 0
    ? Math.max(...notes.map(n => Number(n.id)))
    : 0

  return String(maxId + 1)
}