How to Select All Check Boxs of Gridview row on Single Selection of Header Check Box using JavaScript

function chkall(ival)

{

   var f= document.getElementById("GdvStatus");   

for(var i=0; i<f.getElementsByTagName("input").length ;i++ )

 {

if(f.getElementsByTagName("input").item(i).type == "checkbox" )

   {       

                     f.getElementsByTagName("input").item(i).checked=ival;                

   }  

  } 

}

How To Call:

<asp:CheckBox ID="ChkSelectAll" onclick="chkall(this.checked)" runat="server" />