function generateArray(table) {
    var out = [];
    var rows = table.querySelectorAll('tr');
    var ranges = [];
    for (var R = 0; R < rows.length; ++R) {
        var outRow = [];
        var row = rows[R];
        var columns = row.querySelectorAll('td');
        for (var C = 0; C < columns.length; ++C) {
            var cell = columns[C];
            var colspan = cell.getAttribute('colspan');
            var rowspan = cell.getAttribute('rowspan');
            var cellValue = cell.innerText;
            if(cellValue !== "" && cellValue == +cellValue) cellValue = +cellValue;

            //Skip ranges
            ranges.forEach(function(range) {
                if(R >= range.s.r && R <= range.e.r && outRow.length >= range.s.c && outRow.length <= range.e.c) {
                    for(var i = 0; i <= range.e.c - range.s.c; ++i) outRow.push(null);
                }
            });

            //Handle Row Span
            if (rowspan || colspan) {
                rowspan = rowspan || 1;
                colspan = colspan || 1;
                ranges.push({s:{r:R, c:outRow.length},e:{r:R+rowspan-1, c:outRow.length+colspan-1}});
            };

            //Handle Value
            outRow.push(cellValue !== "" ? cellValue : null);

            //Handle Colspan
            if (colspan) for (var k = 0; k < colspan - 1; ++k) outRow.push(null);
        }
        out.push(outRow);
    }
    return [out, ranges];
};

function datenum(v, date1904) {
    if(date1904) v+=1462;
    var epoch = Date.parse(v);
    return (epoch - new Date(Date.UTC(1899, 11, 30))) / (24 * 60 * 60 * 1000);
}

function sheet_from_array_of_arrays(data, opts) {
    var ws = {};
    var range = {s: {c:10000000, r:10000000}, e: {c:0, r:0 }};
    for(var R = 0; R != data.length; ++R) {
        for(var C = 0; C != data[R].length; ++C) {
            if(range.s.r > R) range.s.r = R;
            if(range.s.c > C) range.s.c = C;
            if(range.e.r < R) range.e.r = R;
            if(range.e.c < C) range.e.c = C;
            var cell = {v: data[R][C] };
            if(cell.v == null) continue;
            var cell_ref = XLSX.utils.encode_cell({c:C,r:R});

            if(typeof cell.v === 'number') cell.t = 'n';
            else if(typeof cell.v === 'boolean') cell.t = 'b';
            else if(cell.v instanceof Date) {
                cell.t = 'n'; cell.z = XLSX.SSF._table[14];
                cell.v = datenum(cell.v);
            }
            else cell.t = 's';

            ws[cell_ref] = cell;
        }
    }
    if(range.s.c < 10000000) ws['!ref'] = XLSX.utils.encode_range(range);
    return ws;
}

function Workbook() {
    if(!(this instanceof Workbook)) return new Workbook();
    this.SheetNames = [];
    this.Sheets = {};
}

function s2ab(s) {
    var buf = new ArrayBuffer(s.length);
    var view = new Uint8Array(buf);
    for (var i=0; i!=s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
    return buf;
}

function export_table_to_excel(id) {
    var theTable = document.getElementById(id);
    var oo = generateArray(theTable);
    var ranges = oo[1];

    /* original data */
    var data = oo[0];
    var ws_name = "SheetJS";
    console.log(data);

    var wb = new Workbook(), ws = sheet_from_array_of_arrays(data);

    /* add ranges to worksheet */
    ws['!merges'] = ranges;

    /* add worksheet to workbook */
    wb.SheetNames.push(ws_name);
    wb.Sheets[ws_name] = ws;

    var wbout = XLSX.write(wb, {bookType:'xlsx', bookSST:false, type: 'binary'});

    saveAs(new Blob([s2ab(wbout)],{type:"application/octet-stream"}), "test.xlsx")
}