I've got a question regarding storing Data in node-red.
I have a Wallbox with an endpoint that delivers the amount of energy in kWh used. Every day this amount grows.
I already thought about storing the "yesterday" value in a global and substract it from "today" to receive the amount used "today". That would deliver me the amount used on every day, which I want to display. When I do that every day I'd have a nice chart of the amount used from day to day and can also add the values up to see the amount for each month.
Unfortunately I am not sure how to store the date in node-red for this feature. As far as I know I have only standard varialbes that I can use - no arrays or anything like that. Or am I able to create an array , maybe a JSON? and store it to a standard global variable? I would need to parse it afterwards to inject it to the chart everytime.
I am not quite sure if this would be possible in node-red. Any recommendations?
Thx for any hints.