• This widget will only work in tablesorter version 2.8+ and jQuery version 1.7+.
• Please do not use this widget in very large tables (it might be really slow) or when your table includes multiple tbodies.
• In v2.15.6, added group_saveGroups & group_saveReset options. More details are included in the "Options" section.
• In v2.14, added group_dateString option. More details are included in the "Options" section.
• In v2.13, added group_separator option & group-separator-# header class name. To see this in action, check out the file type parser demo.
• In v2.12, added group_callback & group_complete options. See options section below for details.
• In v2.11:
  • The grouping widget now works across multiple tbodies.
  • Added group-false header option which disables the grouping widget for a specific column.
  • Added the group_collapsed option - get more details in the options block below.
  • You can now toggle all group rows by holding down the Shift key while clicking on a group header.
  • This widget now works properly with the pager addon (pager addon updated).
• Clicking on any of the sortable header cells will cause the column below it to sort and add a group header.

Group widget default options (added inside of tablesorter widgetOptions)

group_formatter : function(txt, col, table, c, wo) {
  // If there are empty cells, name the group "Empty"
  return txt === "" ? "Empty" : txt;
}

group_callback : function($cell, $rows, column, table){
  $cell.find('.group-name').append(' group'); // adds "group" to the end of the group name
}

$('table').on('groupingComplete', function(){
  // always hide empty groups ("Empty" can be added by the group_formatter function)
  $(this).find('.group-header:contains("Empty")').trigger('toggleGroup');
});

// you can just return date, date.toLocaleString(), date.toLocaleDateString() or d.toLocaleTimeString()
group_dateString : function(date) {
  return date.toLocaleString();
}

Group header class names (when changing the grouping, notice that the sort doesn't change, just the position and names of the group headers):

• "group-word" (same as "group-word-1") - group the rows using the first word it finds in the column's parsed data.
• "group-word-n" ("n" can be any number) - group the rows using the nth word in the column*.
• "group-separator" (same as "group-separator-1") - group the rows using the text between the start and first separator that it finds in the column's parsed data (v2.13).
• "group-separator-n" ("n" can be any number) - group the rows using the nth separated group in the column (v2.13)*.
• "group-letter" (same as "group-letter-1") - group the rows using the first letter it finds in the column's parsed data.
• "group-letter-n" ("n" can be any number) - group the rows using letters 1 through n (if n = 2, then it's the first 2 letters) in the column's parsed data.
• "group-number" (same as "group-number-1") - group the rows by the number it finds in the column (step of one).
• "group-number-n" ("n" can be any number) - group the rows into blocks of every n values. So, if n = 10, the groups will be 0-9, 10-19, 20-29, etc
• "group-date" - group the rows by full date (this shows the current UTC time corrected for your time zone)
• "group-date-year" - group the rows by year
• "group-date-month" - group the rows by month*
• "group-date-day" - group the rows by month/day*
• "group-date-week" - group the rows by day of the week*
• "group-date-time" - group the rows by time*
• "group-false" - disable grouping of rows for a column (v2.11).