Gets the dictionary of languages to language codes that Yandex supports.

languageCodes.js

var KEY = '';

var getRequestSync = function(url) {
  var xhr = new XMLHttpRequest();
  var responseText;
  
  xhr.onreadystatechange = function() {
    if (xhr.readyState === XMLHttpRequest.DONE)
      responseText = xhr.status === 200 ? xhr.responseText : null;
  };
    
  xhr.open('GET', url, false);
  xhr.send();
  
  return responseText;
};

var swapKeyValues = function(dict) {
  var d = {};
  for (var key in dict) {
    d[dict[key]] = key;
  }
  return d;
};

var baseUrl = 'https://translate.yandex.net/api/v1.5/tr.json/getLangs';
var url = baseUrl + '?key=' + KEY + '&ui=en';
  
var langCodes = swapKeyValues(JSON.parse(getRequestSync(url)).langs);
console.log(langCodes);