@Hypnos,
I was wondering the same thing last night, because the name "json" already tells everything. But since Node-RED is Javascript objects all over the place, I thought that it had to be a Javascript array (and me using it somehow incorrectly)...
And I was so sure that I already had used it before, but couldn't find anything...
@knolleary: thanks for the explanation and confirmation!
Ah yes Steve,
That is why I couldn't find it anymore. After a heavy day at work completely forgotten about that one...
Every time I look at that functions parameters, I always have to remind myself whether this is used for node or msg fields or both.