Javascript function to check/uncheck all checkboxes in a checkboxlist, this also allows for normally functionality

gistfile1.txt

 function cblNamesChecked(event) {
            var checkBoxList = document.getElementById("<%=cblNames.ClientID %>");
            var checkBoxes = checkBoxList.getElementsByTagName("input");

            event = event || window.event;
            var target = event.target || event.srcElement;

            if (target.id == "cblNames_0") {
                for (var i = 0; i < checkBoxes.length; i++) {
                    checkBoxes[i].checked = target.checked;
                }
            } 
        }
        
<asp:CheckBoxList ID="cblNames" runat="server" CellPadding="0" OnClick="cblNamesChecked(event)" />