There is a Gremlin in this somewhere. I have narrowed it down to messages being received which are not correctly formatted. A valid message should look something like this: {"payload":"16:14:37@6,1","topic":"alarm_clock/text","_msgid":"efc6bef8.efa76","_event":"node:e8276ab2.052ef8"} The part/s …

Yeah, ok. Sorry. Firefox is being a bit difficult to me just now as well. (never rains, it pours!)

undefined, null and "". "" is a String object that contains no characters null is the null object. It exists as a thing and contains no data of any type. undefined means there no object of any sort. As Steve has shared, when you do a Boolean test of them using == they all are equivalent to fal…

it s the opposite use if (!msg.topic) { or if (msg.topic) { ...has topic } else { ... no topic }

Or visually (from various places on internet) :wink: [image] they all == no paper

Simon, for that particular instance (your picture) , remove the ! from the first line and it will work. if ( ! msg.topic ) { should read if ( no topic ) { then where as if ( msg.topic ) { should read if ( has topic ) { then

[image] cymplecy: I'm not getting a different output when one message has no topic and one message has msg.topic = "" you shouldnt for the if(msg.topic) test as "" and missing will both fail the test. Perhaps I am missing the requirement? I thought Andrew wanted to check a topic was "somethi…

Ok, just to clarify - sorry folks. If a message is going through the system I need to catch it if things go awry. So I have an output (input... what ever) which is the message which is non-compliant to a condition. If it is, I want to see what the original message is/was that was sent. So: The O…

[image] cymplecy: [image] In the sense that ... if (msg.topic) { //the topic is something more than "" - lets use it } else { //the topic is either "", null or undefined } As i said Simon, I might have missed Andrews requirement. Nothing to see here folks, move along :crazy_face:

[image] Trying_to_learn: The Original message may (or not) have a defined topic. Not sure if it is null, undefined or "". If I get a message of a non compliant message, I set the topic to "SOMETHING" (as in it has something in its field.) In which case, as I said before... if (msg.topic) { …

Node-RED

Node-RED Forum

Need help with how to do this

General

system Closed 31 July 2021 08:46 32

This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.

Topic		Replies	Views
Simple repeat last msg node to re-send MQTT General	26	2785	2 September 2020
How to Only respond to 2nd message (within time window) General	16	1654	28 April 2025
Unexpected token D in JSON at position 0 General	47	6278	12 June 2020
Topic getting lost/overridden General	9	823	30 May 2019
Data Fetch / Persistency General function-node	12	330	7 March 2024

Copyright OpenJS Foundation and Node-RED contributors. All rights reserved. The OpenJS Foundation has registered trademarks and uses trademarks. For a list of trademarks of the OpenJS Foundation, please see our Trademark Policy and Trademark List. Trademarks and logos not indicated on the list of OpenJS Foundation trademarks are trademarks™ or registered® trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

Need help with how to do this

Related topics