I Import Excel Into Gridview, I Want To Get Cells Value In This Gridview Using Javascript But I Impossible, Please Help Me!

var gvtable = document.getElementById('<%=GridView1.ClientID %>');

        for (var row = 1; row < gvtable.rows.length; row++){

          for (var col = 0; col < gvtable.rows[row].cells.length; col++){
              gvtable.rows[row].cells[col].textContent;
           }
       }