Gridview Header CheckBox click selects all the item CheckBoxes

Below is the JavaScript function which is responsible to Select or Deselect all the CheckBoxes when Header CheckBox is clicked....
HeaderCheck(CheckBox)
{
cnt=0;
var TargetBaseControl = document.getElementById('ctl00_ContentPlaceHolder1_GridView1');
var TargetChildControl = 'ChkSel';
var Inputs = TargetBaseControl.getElementsByTagName('input');
for(var n = 0; n < type ="=">= 0)
{
Inputs[n].checked = CheckBox.checked;
}
}

Call this function in GridView's Header CheckBox onclick............Below is the code snippet
asp:templatefield
headertemplate
asp:templatefield
headertemplate
asp:checkbox id="ChkHeader" runat="server" onclick="return HeaderCheck(this);"
asp:checkbox
itemtemplate
asp:checkbox id="ChkSel" runat="server"
asp:checkbox
itemtemplate
headertemplate asp:templatefield
asp:checkbox id="ChkHeader" runat="server" onclick="return HeaderCheck(this);"
asp:checkbox
itemtemplate
asp:checkbox id="ChkSel" runat="server"
asp:checkbox
itemtemplate
headertemplate asp:templatefield