Задание №2

gistfile1.js

/**
 * Реализация API, не изменяйте ее
 * @param {string} url
 * @param {function} callback
 */
function getData(url, callback) {
    var RESPONSES = {
        '/countries': [
            {name: 'Cameroon', continent: 'Africa'},
            {name :'Fiji Islands', continent: 'Oceania'},
            {name: 'Guatemala', continent: 'North America'},
            {name: 'Japan', continent: 'Asia'},
            {name: 'Yugoslavia', continent: 'Europe'},
            {name: 'Tanzania', continent: 'Africa'}
        ],
        '/cities': [
            {name: 'Bamenda', country: 'Cameroon'},
            {name: 'Suva', country: 'Fiji Islands'},
            {name: 'Quetzaltenango', country: 'Guatemala'},
            {name: 'Osaka', country: 'Japan'},
            {name: 'Subotica', country: 'Yugoslavia'},
            {name: 'Zanzibar', country: 'Tanzania'},
        ],
        '/populations': [
            {count: 138000, name: 'Bamenda'},
            {count: 77366, name: 'Suva'},
            {count: 90801, name: 'Quetzaltenango'},
            {count: 2595674, name: 'Osaka'},
            {count: 100386, name: 'Subotica'},
            {count: 157634, name: 'Zanzibar'}
        ]
    };
 
    setTimeout(function () {
        var result = RESPONSES[url];
        if (!result) {
            return callback('Unknown url');
        }
 
        callback(null, result);
    }, Math.round(Math.random * 1000));
}
 
/**
 * Ваши изменения ниже
 */
var requests = ['/countries', '/cities', '/populations'];
var responses = {};

var input = window.prompt('Input something (city, country or continent):'); // may be 'Africa'

function _exist(object){
  return function(key){
    return object.hasOwnProperty(key);
  };
}

function _compare(value, key){
  return function(element){
    return value === (key ? element[key] : element);
  };
}

function _compareSome(array, key){
  return function(element){
    return array.some(_compare(key ? element[key] : element));
  };
}

function _add(key){
  return function(result, element){
    return result += element[key];
  };
}

function _get(key){
  return function(element){
    return element[key];
  };
}

function getPopulations(data, input){
  var populations,
      countries,
      cities;

  // search input in cities
  populations = data['/populations']
    .filter(_compare(input, 'name'));

  if (populations.length) {
    return populations;
  }

  // search input in countries
  cities = data['/cities']
    .filter(_compare(input, 'country'))
    .map(_get('name'));

  populations = data['/populations']
    .filter(_compareSome(cities, 'name'));

  if (populations.length) {
    return populations;
  }

  // search input in continents
  countries = data['/countries']
    .filter(_compare(input, 'continent'))
    .map(_get('name'));

  cities = data['/cities']
    .filter(_compareSome(countries, 'country'))
    .map(_get('name'));

  populations = data['/populations']
    .filter(_compareSome(cities, 'name'));

  if (populations.length) {
    return populations;
  }

  return [];
}

requests.forEach(function(request){
  getData(request, function(error, result){
    responses[request] = result;

    // check all responses
    if ( requests.every(_exist(responses)) ) {
      var population = getPopulations(responses, input).reduce(_add('count'), 0);
      console.log('Total population in', input, ':', population);
    }
  }); 
})


// Проблема кода была в том что цикл for не создает скоп для каждого прохода
// и в момент выполнения callback переменная request будет всегда ссылаться
// на requests[3]

// Простой способ починить - обернуть тело цикла в самовызывающуюся функцию 

// ugly code
/*
for (i = 0; i < 3; i++) {

  (function(){

    var request = requests[i];
    var callback = function (error, result) {
        responses[request] = result;
        var l = [];
        for (K in responses)
            l.push(K);
 
        if (l.length == 3) {
            var c = [], cc = [], p = 0;
            for (i = 0; i < responses['/countries'].length; i++) {
                if (responses['/countries'][i].continent === 'Africa') {
                    c.push(responses['/countries'][i].name);
                }
            }
 
            for (i = 0; i < responses['/cities'].length; i++) {
                for (j = 0; j < c.length; j++) {
                    if (responses['/cities'][i].country === c[j]) {
                        cc.push(responses['/cities'][i].name);
                    }
                }
            }
 
            for (i = 0; i < responses['/populations'].length; i++) {
                for (j = 0; j < cc.length; j++) {
                    if (responses['/populations'][i].name === cc[j]) {
                        p += responses['/populations'][i].count;
                    }
                }
            }
 
            console.log('Total population in African cities: ' + p);
        }
    };
 
    getData(request, callback);

  })();

}
*/