Code for the async/await episode of Fun Fun Function.

example01.js

const response = await fetch(`https://catappapi.herokuapp.com/users/${userId}`)
  const data = await response.json()
  return data.imageUrl
}

example02.js

const response = await fetch(`https://catappapi.herokuapp.com/users/${userId}`)
  const data = await response.json()
  return data.imageUrl
}

example03.js

function fetchCatAvatars(userId) {
  return fetch(`https://catappapi.herokuapp.com/users/${userId}`)
    .then(response => response.json())
    .then(user => {
      const promises = user.cats.map(catId => 
        fetch(`https://catappapi.herokuapp.com/cats/${catId}`)
          .then(response => response.json())
          .then(catData => catData.imageUrl))
      return Promise.all(promises)
    })
}

example04.js

async function fetchCatAvatars(userId) {
  const response = await fetch(`http://catappapi.herokuapp.com/users/${userId}`)
  const user = await response.json()
  const catImageUrls = []
  for (const catId of user.cats) {
    const response = await fetch(`http://catappapi.herokuapp.com/cats/${catId}`)
    const catData = await response.json() 
    catImageUrls.push(catData.imageUrl)
  }
  return catImageUrls
}

example05.js

async function fetchCatAvatars(userId) {
  const response = await fetch(`http://catappapi.herokuapp.com/users/${userId}`)
  const user = await response.json()

  return await Promise.all(user.cats.map(async function(catId) {
    const response = await fetch(`http://catappapi.herokuapp.com/cats/${catId}`)
    const catData = await response.json() 
    return catData.imageUrl
  }))
}

example06.js

async function fetchCatAvatars(userId) {
  const response = await fetch(`http://catappapi.herokuapp.com/users/${userId}`)
  const user = await response.json()

  return await Promise.all(user.cats.map(async function(catId) {
    const response = await fetch(`http://catappapi.herokuapp.com/cats/${catId}`)
    const catData = await response.json() 
    return catData.imageUrl
  }))
}

example07.js

const processUser = require('imaginary_service/process_user')

async function processAllUsers () {
  const sql = 'SELECT id FROM users'
  const users = await db.query(sql, [])
  for (const user of users) {
    await processUser(user.id)
  }
}

example08.js

const processUser = require('imaginary_service/process_user')

function processAllUsers () {
  const sql = 'SELECT id FROM users'
  return db.query(sql, [])
    .then(users => 
      users.reduce((lastPromise, user) => 
        lastPromise.then(_ => processUser(user.id))
      , Promise.resolve()))
}

fake-api-service.js

var restify = require('restify')
const corsMiddleware = require('restify-cors-middleware')



const db = {
  users: {
    '123': {
      name: 'mpj',
      cats: [ 21, 33, 45 ],
      imageUrl: 'http://images.somecdn.com/user-123.jpg'
    }
  },
  cats: {
    '21': {
      name: 'Fluffykins',
      imageUrl: 'http://images.somecdn.com/cat-21.jpg',
    },

    '33': {
      name: 'Waffles',
      imageUrl: 'http://images.somecdn.com/cat-33.jpg'
    },

    '45': {
      name: 'Sniffles', 
      imageUrl: 'http://images.somecdn.com/cat-45.jpg'
    }    
  }
}

function cats(req, res, next) {
  res.send(db.cats[req.params.id])
  next()
}

function users(req, res, next) {
  res.send(db.users[req.params.id])
  next()
}

var server = restify.createServer()

const cors = corsMiddleware({
  origins: ['*']
})
server.pre(cors.preflight)
server.use(cors.actual)

server.get('/cats/:id', cats)
server.get('/users/:id', users)

server.listen(process.env.PORT || 8080, function() {
  console.log('%s listening at %s', server.name, server.url)
})

In example05 and example06:

 return await Promise.all(user.cats.map(async function(catId) {
   // ...
 }))

is the same as:

 return Promise.all(user.cats.map(async function(catId) { // without await
   // ...
 }))

Because Promise.all() returns a Promise without await keyword. If you use await you will return a value instead of a promise. It works as well but there is a little difference behind.

Great show @mpj! I'm a big fan of yours.

Any reason why example01.js and example02.js are the same ?