Change the Text of an asp:CheckBox when clicked

<asp:CheckBox ID="CheckBox1" runat="server" Text="Open" />

function changeCheckboxText(checkbox)
{
  if (checkbox.checked)
    checkbox.nextSibling.innerHTML = 'on text';
  else
    checkbox.nextSibling.innerHTML = 'off text';
}

<asp:CheckBox runat="server" ID="chkTest" onclick="changeCheckboxText(this);" />

$("input[id$=CheckBox1]").click(function() {
    if ($(this).attr("checked")) {
        $(this).next("label:first").text("Open");
    }
    else {
        $(this).next("label:first").text("Close");
    }
});

CheckBox1.Attributes.Add("JavaScipt")