Making seen feature for conversejs?

I am working on seen feature for boxchat of conversejs , I create a function when gender the messages will check , if not viewed will send the viewed message , I have successfully sent the newsletter but I don't know in the right message_text function how to call the seen save function. someone please help me.

const sendSeen = el => {

      if (el.model.get("sender") == "them" && !el.model.get('seen')) {
        console.log(el.model);
        const msg = model_$msg({
          'from': shared_converse.connection.jid,
          'id': model_u.getUniqueId(),
          'to': el.model.get("from"),
          'type': 'chat'
        }).c('seen', {
          'xmlns': "urn:xmpp:ringme:seen",
          'id': el.model.get("msgid")
        }).up().c('store', {
          'xmlns': model_Strophe.NS.HINTS
        }).up()
          .c('contentType', {
            'xmlns': "urn:xmpp:ringme:contentType",
            'name': "seen"
          }).root();
        core_api.send(msg);

        const message = this.messages.findWhere({
          'msgid': el.model.get("msgid")
        });
        // headless_log.log("handleSeen -> message: " + JSON.stringify(message));
        if (message && !message.get('seen')) {
          message.save({
            'seen': new Date().toISOString()
          });
        }
        return;
      }

    }

I don't know how to get const message