Determening which cell is clicked and the header of the column

Going with Sergey's assumption that we're talking about front-end code, I will continue down that path and give a JQuery solution, as it sounds like your roadblock is how to traverse the DOM to find the corresponding first column TD.

To get the contents of the first TD of the row containing the TD clicked, you could use

var firstItem = $(this).closest('tr').children(':first-child').html();

The code could be simplified if the first TD isn't itself clickable:

var firstItem = $(this).siblings(':first-child').html();