How to get VK user avatar in iframe app?

Question

API

Good morning. After a long search, I could not find the answer to the question.

Answer 1

is = {
  type: function (value, type) {return {}.toString.call(value).match(/ ([a-z]+)/i)[1] == type}
}

registry = {}

function API_request(method, parameters, success, error) {
  if (!is.type(parameters, "Object")) {
    console.error("parameters must be an object.")

    return
  }

  var callback = "c" + String(Math.random()).slice(-6)
  var flag = false

  registry[callback] =
    function (data) {
      flag = true

      delete registry[callback]

      if (is.type(success, "Function")) {success(data)}
    }

  var URL = "https://api.vk.com/method/" + method + "?"

  for (var key in parameters) {URL += key + "=" + parameters[key] + "&"}

  var script = document.createElement("script")

  script.src = URL + "callback=registry." + callback

  script.onload = script.onerror =
    function () {
      if (flag) {return}

      delete registry[callback]

      if (is.type(error, "Function")) {error()}
    }

  document.head.appendChild(script)
}

API_request(
  "users.get",

  {
    user_ids: "1,2,3",
    fields: "photo_50"
  },

  function (response) {
    for (i = 0; i < response.response.length; i++) {
      img = document.createElement("img")

      img.src = response.response[i].photo_50

      document.body.appendChild(img)
    }
  },

  function () {alert("An error occured. No data loaded.")}
)

Answer 2

It can be even simpler, everything works. But! I can't pull out a local variable with the result from the function and make it global. Please tell me, is it possible to write this one here - result.response[0]['first_name'], somehow write it to a global variable, I've already tried everything (

var api= "https://api.vk.com/method/users.get?user_id=1&v=5.45&callback=callbackFunc";
var script= document.createElement('SCRIPT'); 
script.src= api; 
document.getElementsByTagName("head")[0].appendChild(script); 


function callbackFunc(result) { 
alert(result.response[0]['first_name']);
}