function pget(url) {

        return new Promise(function (resolve, reject) {

            var req = new XMLHttpRequest();

            req.open('GET', url);

            req.onload = function () {

                if(req.status==200){

                    resolve(req.response);

                }

                else {

                    reject(Error(req.statusText));

                }

            };

            req.onerror = function () {

                reject(Error("Network Error"));

            };

            req.send();

        });

    }

    function pgetJSON(url) {

        return pget(url).then(JSON.parse);

    }

function getJokeCategories(){

    var jokesToGet = [];

    var result = {};

    Promise.all(

        [pgetJSON("http://api.icndb.com/categories").then(function(data){

            result.cats = data.value;

        }),

        pgetJSON("http://api.icndb.com/jokes/count").then(function(data){

            for(var i=15; i<20; i++){

                jokesToGet.push("http://api.icndb.com/jokes/"+i);

            }

            result.jokes = jokesToGet;

            Promise.all(

                jokesToGet.map(function(jk){

                    pgetJSON(jk).then(function(joke){

                        console.log(joke, " just returned");

                    });

                })

            ).then(function(){

                console.log("All jokes returned. This should actually happen only when all jokes are retireved.");

            });

        })

        ]

    ).then(function(){

        console.log(result, "This should happen at the very end when joke count, joke categories and all jokes are returned.");

    });

}

getJokeCategories();