In node red, how can I watch the value of a global variable and do something with it when the value changes? I'm building an application that has a front-end user interface, and a sort of back end that does a control loop with values set by the user. I would like to keep my flows separate by setting…

Instead of using globals, you could use Retained Topics in MQTT. Then, on startup and whenever it changes, all connected nodes will be sent a message.

To directly answer your question, you cannot. I've long wanted to write a context handler that did have notifications but though I started a couple of times, I fear neither my Node-fu nor my patience was sufficient. So I'm afraid that it remains a theory. Your best bet is, as Colin says, to use MQT…

[image] joshk: In node red, how can I watch the value of a global variable and do something with it when the value changes? Inside the function node, you can access the global context, which may be considered a global variable for the intentions of what you may be doing. Then, it's just a mat…

Alternatively, of course, you can just use a link node from where the value is changed, to send a message to the node that needs to know.

Here is my method. This will take a minute to explain, so bear with me. I have four possible presence states that dictate what mode my house is in. I'm using Hubitat, iPhones and Withings sleep sensors to set those states. They are home/away or asleep/awake for me and both states again for my wife. …

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Watch Global Variable

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E1cid 18 May 2023 16:59 2

This topic and post may help Lighting controller ideas - #19 by Steve-Mcl

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Watch Global Variable

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