The TR.sectionRowIndex property is the vertical coordinate for cells in this row measured within a THEAD, TBODY or TFOOT group and is reset to zero at the start of each section of the table.

This property yields a zero-based index number for this table row within the rows[] collection belonging to the THEAD, TBODY or TFOOT object the row is a member of.

Note that this index will not hold true for the rows[] collections belonging to TABLE object. For that, you should inspect the rowIndex property.

Property attributes:

ReadOnly.