Here Mudassar Ahmed Khan has explained with an example, how to get RowIndex when CheckBox in GridView Row is Checked (Clicked) using JavaScript.
All the CheckBox inside the GridView will be assigned a Click event handler using JavaScript.
When the CheckBox inside the GridView Row is Checked (Clicked), the GridView Row will be referenced and then the RowIndex and the Row (Cell) values will be extracted and displayed using JavaScript Alert Message Box.