How access checkbox in javascript

hi to all
i am facing a problem to access a check box in javascript function that checkbox is in repeater controle
as
<asp:Repeater ID="rptCategories" runat="server">
        <ItemTemplate>
          <asp:CheckBox runat="server" ID="chkParentCategory" Text='<%#Eval("CategoryName") %>' />
                                      
             </ItemTemplate>
</asp:Repeater>
how i can access this check box in javascript function

 regards Ahsan
 
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