callback_hell.js

let random_pokemon = []
let image_array = []

$.get('http://pokeapi.co/api/v2/pokemon'
  ).then(
  function(data) {
  let count = data.count
  console.log("Retrieved count")
  return $.get('http://pokeapi.co/api/v2/pokemon/?limit=' + count)
    }
  ).then(
  function(data) {
  console.log("Retrieved all pokemon")
  let all_pokemon = data.results
  random_pokemon = pick_three_randomly(all_pokemon)
  return $.get(random_pokemon[0].url)
    }
  ).then (
    function(pokemon_data) {
     console.log("Retrieved first pokemon")
     add_image_to_array(image_array, pokemon_data)
     return $.get(random_pokemon[1].url)
    }
  ).then (
   function(pokemon_data) {
   console.log("Retrieved second pokemon")
   add_image_to_array(image_array, pokemon_data)
   return $.get(random_pokemon[2].url)
    }
  ).then (
   function(pokemon_data) {
   console.log("Retrieved third pokemon")
   add_image_to_array(image_array, pokemon_data)
   $("body").empty()
   for (let i = 0; i < image_array.length; ++i) {
     let img = image_array[i]
     $("body").append(
       $("<h1>", {text: img.name}),
       $("<img>", {src: img.front}),
       $("<img>", {src: img.back})
     )
   }
})

function add_image_to_array(image_array, pokemon_data) {
  image_array.push({
    name: pokemon_data.name,
    front: pokemon_data.sprites.front_default,
    back: pokemon_data.sprites.back_default
  })
}

function pick_three_randomly(data_array) {
  let chosen = []
  let count = data_array.length
  for (let i = 0; i < 3; ++i) {
    let random_index = Math.floor(Math.random() * count)
    chosen.push( data_array[random_index] )
  }
  return chosen
}