GObject.signal_handler_is_connected

function signal_handler_is_connected(instance: GObject.Object, handler_id: Number(gulong)): Boolean {
    // Gjs wrapper for g_signal_handler_is_connected()
}

Returns whether handler_id is the id of a handler connected to instance.

instance: The instance where a signal handler is sought.
handler_id: the handler id.
Returns: whether handler_id identifies a handler connected to instance.