Devextreme Display database results in Selectbox

Question

I have searched this site and tried, but I am still not coming right. I have searched these threads (among others):

How to get return value in a function with inside Ajax call - JQuery

get return value of jQuery get().done() function

I have one page on my app. I have one dxSelectBox on my page. I need to display a list of depots inside the dxSelectBox. My Webservice works. I am trying this to show the results in the dxSelectBox but it does not show anything:

App.FirstScreen = function (params) {
    // "use strict";
    var viewModel = {
        dsDepots: ko.observableArray([]),
        GetDepots: getDepots (),
    };
    return viewModel;
};

function getDepots() {
    // this will generate another thread to run in another function
    jQuery.ajax({
        url: 'connection_string + "/rest/_getDepots"',
        type: 'get',
        success: function (data) {
            if (data != "") {
                var _result = JSON.parse(data.childNodes['0'].childNodes['0'].data);
                viewModel.dsDepots(_result);
            }
            return (data);
        },
        error: function () {
            return "Hello";
        }
    });
}