Dmitriy Mozgovoy

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 = {}; //, counter=0;

       for (var i = 0; i < 3; i++) {
           var _request = requests[i];

           var callback = function(request){
               return function (error, result) {

                   responses[request] = result;

                   var i, j;

                   if (Object.keys(responses).length == 3) { //or counter++==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);
                   }
               }
           }(_request);


           getData(_request, callback);
       }

var requests = ['/countries', '/cities', '/populations'];
       var responses = {};

       function load(request){
           return new Promise(function(resolve,reject){
               getData(request,function(error, result){
                    if(!error){
                        resolve(result);
                    }else{
                        reject (error);
                    }
               })
           });
       }

       function getPopulation(state){

           return Promise.all(requests.map(function(request){
               return load(request);
           })).then(function(data){
               //console.log(arguments);
               var countries=data[0],
                   cities=data[1],
                   populations=data[2],
                   result;

               console.log(countries,cities,populations);

               //calc here for state

               return result;

           },function(error){
               console.warn("Data error",error);
           });
       }

       getPopulation("Africa").then(console.log);

function loadScript(src,_timeout) {

           return new Promise(function(resolve, reject){
               if(!src){
                   reject(new TypeError("filename is missing"));
                   return;
               }

               var script=document.createElement("script"),
                   timer,
                   head=document.getElementsByTagName("head")[0];


               head.appendChild(script);

               function leanup(){
                   clearTimeout(timer);
                   timer=null;
                   script.onerror=script.onreadystatechange=script.onload=null;
               }

               function onload(){
                   leanup();
                   if(!script.onreadystatechange||(script.readyState&&script.readyState=="complete")){
                       resolve(script);
                   }
               }

               script.onerror=function(error){
                   leanup();
                   head.removeChild(script);
                   script=null;
                   reject(new Error("network"));
               };

               if (script.onreadystatechange === undefined) {
                   script.onload = onload;
               } else {
                   script.onreadystatechange = onload;
               }

               timer=setTimeout(script.onerror,_timeout||30000);
               script.setAttribute("type", "text/javascript");
               script.setAttribute("src", src);
           });
       }

       function loadCSS(src, _timeout) {
           var css = document.createElement('link'), c = 1000;
           document.getElementsByTagName('head')[0].appendChild(css);
           css.setAttribute("rel", "stylesheet");
           css.setAttribute("type", "text/css");


           return new Promise(function(resolve, reject){
               var c=(_timeout||10)*100;
               if(src) {
                   css.onerror = function (error) {
                       if(timer)clearInterval(timer);
                       timer = null;

                       reject(new Error("network"));
                   };

                   var sheet, cssRules, timer;
                   if ('sheet' in css) {
                       sheet = 'sheet';
                       cssRules = 'cssRules';
                   }
                   else {
                       sheet = 'styleSheet';
                       cssRules = 'rules';
                   }
                   timer = setInterval(function(){
                       try {
                           if (css[sheet] && css[sheet][cssRules].length) {
                               clearInterval(timer);
                               timer = null;
                               resolve(css);
                               return;
                           }
                       }catch(e){}

                       if(c--<0){
                           clearInterval(timer);
                           timer = null;
                           reject(new Error("timeout"));
                       }
                   }, 10);

                   css.setAttribute("href", src);
               }else{
                   reject(new TypeError("filename is missing"));
               }
           });
       }

loadScript("/engine/classes/js/jquery.pickmeup.min.js").then(function(){
           console.log("js ready");
       },function(error){
           console.log(error);
       })

       loadCSS("/engine/classes/css/pickmeup.min.css").then(function(){
           console.log("css ready");
       },function(error){
           console.log(error);
       })