callback-hell.js

var init = function () {
    var data1, data2, data3, data4, data5, data6, data7, data8, data9, data10;

    console.log('Start by waiting for a second...');

    window.setTimeout(function() {
        console.log('Then send a GET request to a couple of websites');

        $.get('https://cors-test.appspot.com/test', function (data) {
            data1 = data;

            $.get('https://cors-test.appspot.com/test', function (data) {
                data2 = data;

                $.get('https://cors-test.appspot.com/test', function (data) {
                    data3 = data;

                    $.get('https://cors-test.appspot.com/test', function (data) {
                        data4 = data;

                        $.get('https://cors-test.appspot.com/test', function (data) {
                            data5 = data;

                            $.get('https://cors-test.appspot.com/test', function (data) {
                                data6 = data;

                                $.get('https://cors-test.appspot.com/test', function (data) {
                                    data7 = data;

                                    $.get('https://cors-test.appspot.com/test', function (data) {
                                        data8 = data;

                                        $.get('https://cors-test.appspot.com/test', function (data) {
                                            data9 = data;

                                            $.get('https://cors-test.appspot.com/test', function (data) {
                                                data10 = data;

                                                console.log(data1);
                                                console.log(data2);
                                                console.log(data3);
                                                console.log(data4);
                                                console.log(data5);
                                                console.log(data6);
                                                console.log(data7);
                                                console.log(data8);
                                                console.log(data9);
                                                console.log(data10);
                                            });
                                        });
                                    });
                                });
                            });
                        });
                    });
                });
            });

        });

    }, 1000);
};

init();

generators.js

var init = sync(function* (resume) {
    var data1, data2, data3, data4, data5, data6, data7, data8, data9, data10;

    console.log('Start by waiting for a second...');

    yield sleep(1000, resume);

    console.log('Then send a GET request to a couple of with XMLHttpRequest');

    data1 = yield get('https://cors-test.appspot.com/test', resume);
    data2 = yield get('https://cors-test.appspot.com/test', resume);
    data3 = yield get('https://cors-test.appspot.com/test', resume);
    data4 = yield get('https://cors-test.appspot.com/test', resume);
    data5 = yield get('https://cors-test.appspot.com/test', resume);
    data6 = yield get('https://cors-test.appspot.com/test', resume);
    data7 = yield get('https://cors-test.appspot.com/test', resume);
    data8 = yield get('https://cors-test.appspot.com/test', resume);
    data9 = yield get('https://cors-test.appspot.com/test', resume);
    data10 = yield get('https://cors-test.appspot.com/test', resume);

    console.log(data1);
    console.log(data2);
    console.log(data3);
    console.log(data4);
    console.log(data5);
    console.log(data6);
    console.log(data7);
    console.log(data8);
    console.log(data9);
    console.log(data10);
});

init();