Sum of table rows in Javascript and format cell numbers.

table_sum_rows.js

function prettify (num, separator) {
    var n = (typeof num === "string") ? num : num.toString();
    var sep = typeof separator === "undefined" ? " " : separator;
    return n.replace(/(\d{1,3}(?=(?:\d\d\d)+(?!\d)))/g, "$1" + sep);
}

// SUMM TABLE ROWS
function sumTableRows() {
    var table = document.getElementById("mainTab");
    let lastRow = table.rows[table.rows.length - 1];
    for (var i = 1; i < table.rows.length - 1; i++) {
        let row = table.rows[i];
        for (var j = 1; j < row.cells.length; j++) {
            let cel = row.cells[j];
            lastRow.cells[j].innerText =
                (Number(lastRow.cells[j].innerText) || 0) +
                (Number(cel.innerText) || 0);
            cel.innerText = prettify(cel.innerText);
        }
    }
    for (var i = 1; i < lastRow.cells.length; i++) {
        let cel = lastRow.cells[i];
        cel.innerText = prettify(cel.innerText);
    }
}

$(document).ready(function() {
    sumTableRows();
});

var table = $.parseHTML(
   `<table id="mainTab" style="width:100%" class="table table-striped table-bordered">
    <thead>
      <tr>
        <th>А</th>
        <th>Н</th>
        <th>О</th>
        <th>З</th>
        <th>И</th>
      </tr>
    </thead>
    <tbody>
    </tbody>
    </table>`
);
var rows = $.parseHTML(response.html);
$(table).find('tbody').append($(rows));
$(table).find('tr:last').after('<tr><th>Итого</th><th></th><th></th><th></th><th></th></tr>');