const dateRangeReg = /(\d{2}\s\d{4})?\s?\.\.\s?(\d{2}\s\d{4})?/;
            function isDateRange(str) {
                var re = new RegExp(dateRangeReg);
                return re.test(str);
            }

            function changeFormat(oldFormatDate){
                return oldFormatDate.slice(3) + "-" + oldFormatDate.substr(0, 2);
            }

            function compareDateRanges(first, second) {
                var periodsFirst = first.split(/\s?\.\.\s?/);
                var periodsSecond = second.split(/\s?\.\.\s?/);

                if ((periodsFirst[0] === "") && (periodsSecond[0] !== "")) {
                    return false;
                }
                if ((periodsFirst[0] !== "") && (periodsSecond[0] === "")) {
                    return true;
                }
                if ((periodsFirst[0] === "") && (periodsSecond[0] === "")) {
                    var ldf = new Date(periodsFirst[1]).getTime();
                    var lds = new Date(periodsSecond[1]).getTime();
                    return  ldf > lds;
                }

                periodsFirst.forEach(function(period, index){
                    this[index] = changeFormat(period);
                }, periodsFirst);

                periodsSecond.forEach(function(period, index){
                    this[index] = changeFormat(period);
                }, periodsSecond);

                var firstFromDate = new Date(periodsFirst[0]).getTime();
                var secondFromDate = new Date(periodsSecond[0]).getTime();

                if (firstFromDate === secondFromDate) {
                    if (periodsSecond[1] === "") {
                        return true;
                    }
                    if (periodsFirst[1] === "") {
                        return false;
                    }
                    var firstLastDate = new Date(periodsFirst[1]).getTime();
                    var secondLastDate = new Date(periodsSecond[1]).getTime();
                    return (firstLastDate > secondLastDate)
                } else
                if (firstFromDate > secondFromDate) {
                    return true;
                }
                return false;
            }


            function isBigger(first, second) {
                if (second === "") {
                    return first !== "";
                }
                if (first === "") return false;

                if (parseInt(first).toString().length === first.length) {
                    return  parseInt(first) > parseInt(second);
                }

                if (isDateRange(first)) {
                    return compareDateRanges(first, second);
                }

                return first.toLowerCase() > second.toLowerCase();
            }

            function setArrow(table, num, dir) {
                var column = table.getElementsByTagName("tr")[0].getElementsByTagName("th")[num].innerHTML;
                if (dir === 'desc') {
                    column = column + '▼';
                } else if (dir === 'asc') {
                    column = column + '▲';
                }
                table.getElementsByTagName("tr")[0].getElementsByTagName("th")[num].innerHTML = column;
            }

            function removeAllArrows(table) {
                const regArrow = /(▼)|(▲)/;
                var column = table.getElementsByTagName("tr")[0].getElementsByTagName("th");
                for (var i = 1; i < column.length - 1; i++) {
                    var str = column[i].innerHTML;
                    str = str.replace(regArrow, "");
                    table.getElementsByTagName("tr")[0].getElementsByTagName("th")[i].innerHTML = str;
                }
            }

            function sortTable(num) {
                var table, rows, switching, i, first, second, shouldSwitch, dir, switchcount = 0;
                table = document.getElementById("gens");
                removeAllArrows(table);
                switching = true;
                dir = "asc";
                while (switching) {
                    switching = false;
                    rows = table.getElementsByTagName("tr");
                    for (i = 1; i < (rows.length - 1); i++) {
                        shouldSwitch = false;
                        first = rows[i].getElementsByTagName("td")[num].innerHTML;
                        second = rows[i + 1].getElementsByTagName("td")[num].innerHTML;
                        if (dir === "asc") {
                            if (isBigger(first, second)) {
                                shouldSwitch = true;
                                break;
                            }
                        } else if (dir === "desc") {
                            if (isBigger(second, first)) {
                                shouldSwitch = true;
                                break;
                            }
                        }
                    }
                    if (shouldSwitch) {
                        rows[i].parentNode.insertBefore(rows[i + 1], rows[i]);
                        switching = true;
                        switchcount ++;
                    } else {
                        if (switchcount === 0 && dir === "asc") {
                            dir = "desc";
                            switching = true;
                        }
                    }
                }
                setArrow(table, num, dir);
                for (i = 1; i < rows.length; i++) {
                    rows[i].getElementsByTagName("td")[0].innerHTML = i;
                }
            }