I think the interactive mode is a really neat feature. Looks like this tool fx was likely inspired a bit by jq [1] which is a great library as well. Mainly the dot identity syntax made me think fx might have gotten inspiration from jq. fx definitely seems more approachable to current JS developers than jq. Overall great job on the library!
The links at the bottom are all interesting. Specially jl[1], which uses a functional, Haskell-like language.
The wrong one is the link to jid, which has a very poor language that claims to be like jq, but actually is just dot syntax and nothing else. jiq[2], my fork, has real jq underneath, so may be better, although it has some rough edges waiting to be polished.
It's kinda odd to write imperative expressions like for-loops all in one line without brackets, also the necessity of 'this'. I guess these are the downsides of using a Javascript-like language.
I was about to write this off as a jq clone but it is MUCH more that than! Looks pretty cool, I've installed it for the next time I work with JSON in the CLI.
[1]: https://stedolan.github.io/jq/