Merge table cell by key column

merge_cell.js

// Merge table cell by cell value,
// dependent or independent to other column
// jQuery is required.

// Eg: Table has 2 col: Date and Fullname
// |----------------------------|
// |  Date        |  Fullname   |
// |--------------|-------------|
// |  2012/11/01  |  ManhDV     |
// |--------------|-------------|
// |  2012/11/01  |  ManhDV     |
// |--------------|-------------|
// |  2012/11/01  |  ManhDV     |
// |--------------|-------------|
// |  2012/11/02  |  ManhDV     |
// |--------------|-------------|
// |  2012/11/03  |  ManhDV     |
// |--------------|-------------|
// |  2012/11/03  |  ManhDV     |
// |----------------------------|

// So, if merge with independent:
// |----------------------------|
// |  Date        |  Fullname   |
// |--------------|-------------|
// |              |             |
// |              |             |
// |  2012/11/01  |             |
// |              |             |
// |              |             |
// |--------------|             |
// |  2012/11/02  |  ManhDV     |
// |--------------|             |
// |              |             |
// |  2012/11/03  |             |
// |              |             |
// |--------------|-------------|

// Or merge with dependent to Date column:
// |----------------------------|
// |  Date        |  Fullname   |
// |--------------|-------------|
// |              |             |
// |              |             |
// |  2012/11/01  |  ManhDV     |
// |              |             |
// |              |             |
// |--------------|-------------|
// |  2012/11/02  |  ManhDV     |
// |--------------|-------------|
// |              |             |
// |  2012/11/03  |  ManhDV     |
// |              |             |
// |----------------------------|

var table = $('#table');
mergeIndependentCols(table, [1]); // 1st col is Date
mergeDependentCols(table, [2], 1); // 2nd col is Fullname

function mergeIndependentCols(table, independentColumns) {
    independentColumns.forEach(function (col) {
        var prevValue = null;
        var startCol = null;
        var numRow = 1;
        $.each(table.find('tr td:nth-child(' + col + ')'), function (_, columnHtml) {
            var column = $(columnHtml);
            var currentValue = column.text();
            if (currentValue != prevValue) {
                startCol = column;
                numRow = 1;
                prevValue = currentValue;
            } else {
                numRow++;
                startCol.attr('rowspan', numRow);
                column.hide();
            }
        });
    });
}

function mergeDependentCols(table, cols, keyCol) {
    cols.forEach(function (col) {
        var prevValue = null;
        var startCol = null;
        var numRow = 1;
        $.each(table.find('tr td:nth-child(' + col + ')'), function (_, columnHtml) {
            var column = $(columnHtml);
            var keyColumn = column.closest('tr').find('td:nth-child(' + keyCol + ')');
            var currentValue = column.text();
            if (keyColumn.css('display') == 'none') {
                if (currentValue != prevValue) {
                    startCol = column;
                    numRow = 1;
                    prevValue = currentValue;
                } else {
                    numRow++;
                    startCol.attr('rowspan', numRow);
                    column.hide();
                }
            } else {
                startCol = column;
                numRow = 1;
                prevValue = currentValue;
                startCol.attr('rowspan', numRow);
            }
        });
    });
}