How to make the search case insensitive in Jsgrid filter?

Question

I am trying to make the search case insensitive, and I have tried all the solutions that are found in issues, but it's still not working. Here is the code that I have right now, but I want it to be able to search regardless if user types in letters with uppercase or lowercase.

                loadData: function (filter) {
                    criteria = filter;
                    var data = $.Deferred();
                    $.ajax({
                        type: "POST",
                        contentType: "application/json; charset=utf-8",
                        url: "/Admin/getMultiCentreDeals",
                        dataType: "json"
                    }).done(function (response) {
                        var res = [];
                        if (criteria.dealTitle !== "") {
                            response.forEach(function (element) {
                                if (element.dealTitle.indexOf(criteria.dealTitle) > -1) {
                                    res.push(element);
                                    response = res;
                                }
                            }, this);
                        }
                        else res = response;

                        if (criteria.dealSubTitle !== "") {
                            res = [];
                            response.forEach(function (element) {
                                if (element.dealSubTitle.indexOf(criteria.dealSubTitle) > -1)
                                    res.push(element);
                            }, this);
                        }
                        else res = response;

                        if (criteria.dealURL !== "") {
                            res = [];
                            response.forEach(function (element) {
                                if (element.dealURL.indexOf(criteria.dealURL) > -1)
                                    res.push(element);
                            }, this);
                        }
                        else res = response;

                        data.resolve(res);
                    });
                    return data.promise();
                },
            },

Answer 1

                        var res = [];
                        if (criteria.HotelName !== "") {
                            response.forEach(function (element) {
                                if (element.HotelName.toLowerCase().indexOf(criteria.HotelName.toLowerCase()) > -1) {
                                    res.push(element);
                                    response = res;
                                }
                            }, this);
                        }
                        else res = response;