.js

(function ($) {
    $(function () {
        AJS.dialog2.on("show", function (e) {
            var targetId = e.target.id;
            if (targetId == "my-own-dialog") {
                var someDialog = AJS.dialog2(e.target);
                $(e.target).find("#dialog-close-button").click(function (e) {
                    e.preventDefault();
                    someDialog.hide();
                    someDialog.remove();
                });

                $(e.target).find("#button-A").click(function (e) {

                    $.ajax({
                        type: "GET",
                        dataType: "json",
                        "contentType": "application/json",
                        url: AJS.params.baseURL + "/rest/scriptrunner-jira/latest/custom/...",
                        done: function (data) {
                            // do something with data
                        },
                        fail: function(data) {
                            alert("Error: ...");
                        },
                        always: function() {
                            //
                        }
                    })
                });
            }
        });
    });
})(AJS.$);