VS 2008 - Access Checkbox Value Of Gridview In JS

I wnat to access the checkbox value of gridview in JS, using for loop,

function sonia()
{
alert('a');
var gvET='<%=GridView1.ClientID%>';
var grid = document.getElementById(gvET);
var rowIdx=1;
alert (grid.rows.length);
for (rowIdx; rowIdx<=grid.rows.length-1; rowIdx++)
{
var rowElement = grid.rows[rowIdx];
var chkBox = rowElement.cells[0].firstChild;
alert(chkBox.checked);
var chkBox = rowElement.cells[1].firstChild;
alert(chkBox.text);
}
return false ;
}

I set the autogenerate columns porperty of Gridview to true. In first cell i have checkboxes. My code is not giving me any error. First cell value that is checkboxs comes correctlt,but text of second cell is not coming in second alert.Y so? In second alert,everytime undefined is coming