callback-example.js

const request = require('request')

function add (n1, n2) {
  return n1 + n2
}

// /////////////////////////////////////////////////////////////////////
// First Section
// /////////////////////////////////////////////////////////////////////
console.log('before-add') // 1
let sum = add(4, 5)
console.log(sum) // 2
console.log('after-add') // 3

// /////////////////////////////////////////////////////////////////////
// Second Section
// /////////////////////////////////////////////////////////////////////
console.log('before-request') // 4
request('http://localhost:3000/genres', function (error, response, body) {
  console.log('the-real-after-request') // 6
  const genres = JSON.parse(body)
  console.log(genres) // 7
  console.log('after-request-and-parsing') // 8
})
console.log('suppose-to-be-after-request') // 5

/* Output:
before-add
9
after-add
before-request
suppose-to-be-after-request
the-real-after-request
[ { id: 1, name: 'fiction' },
  { id: 2, name: 'history' },
  { id: 3, name: 'science' } ]
after-request-and-parsing
*/