how can I add the data of a variable to an array?

My may be a bit easy, but being new on this topic is a bit complicated.

I have this code

<pre>
<em>
$(document).ready(function() {

        var date = $.getJSON("prueba.php?providerid=157&startdate='2018-04-05'", function(result){

                for (var item in result) {
                    return(result[item]);
                }
            });

            console.log(date);

            $("#select_days").kendoCalendar({
                value: Date(),
                dates: [
                  new Date("2018-5-12"),

                ],
                disableDates: function (date) {
                    var dates = $("#select_days").data("kendoCalendar").options.dates;
                    if (date && compareDates(date, dates)) {
                        return false;
                    } else {
                        return true;
                    }
                }
            });

            function compareDates(date, dates) {
                for (var i = 0; i < dates.length; i++) {
                    if (dates[i].getDate() == date.getDate() &&
                        dates[i].getMonth() == date.getMonth() &&
                        dates[i].getYear() == date.getYear()) {
                      return true
                    }
                }
            }
        });
</em>
</pre>

The idea is that the array dates upload the data that is in the varible date .