docs: @Nonnull
    public final HCHead addJS (@Nonnull final IHCNode aJS)
    {
      ValueEnforcer.notNull (aJS, "JS");
      if (!HCJSNodeDetector.isJSNode (aJS))
        throw new IllegalArgumentException (aJS + " is not a valid JS node!");
      m_aJS.add (aJS);
      return this;
    }