asp.net - Check if asp Checkbox is checked in a row of a GridView with Javascript -

i have grid view , want see if checkbox in first column checked. if check box checked opens new window. cannot figure out how see if checkbox checked. please function below not working , can't figure out why.

function mapselectedclick()      {         var customerids = "";         var grid = document.getelementbyid('<%=grdcustomers.clientid %>');          (var = 1; < grid.rows.length; i++)         {             var row = grid.rows[i];             var customerid = grid.rows[i].cells[1].innertext;             if (grid.rows[i].cell[0].type == "checkbox")             {                 if (grid.rows[i].cell[0].childnodes[0].checked)                 {                     customerids += customerid.tostring() + ',';                 }             }         }          customerids = customerids.substring(0, customerids.length-1);         window.open("mapcustomers.aspx?customerids=" + customerids);     } 

there few problems in code:

1. in both if conditions, used cell[0] instead of cells[0]
2. in outer if condition used cell[0].type == "checkbox". cell can't have type checkbox, includes chekbox control child

modify function this:

function mapselectedclick()  {     var customerids = "";     var grid = document.getelementbyid('<%=grdcustomers.clientid %>');      (var = 1; < grid.rows.length; i++)     {         var row = grid.rows[i];         var customerid = row.cells[1].innertext;         var ctrl = row.cells[0].childnodes[0];         if (ctrl.type == "checkbox")         {             if (ctrl.checked)             {                 customerids += customerid.tostring() + ',';             }         }     }      customerids = customerids.substring(0, customerids.length-1);     window.open("mapcustomers.aspx?customerids=" + customerids); } 

note innertext not cross browser compatible, use innerhtml wherever possible.