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Show HN: JSON Query

(jsonquerylang.org)
147 points wofo | 1 comments | 27 Oct 25 16:22 UTC | HN request time: 1.253s | source

I'm working on a tool that will probably involve querying JSON documents and I'm asking myself how to expose that functionality to my users.

I like the power of `jq` and the fact that LLMs are proficient at it, but I find it right out impossible to come up with the right `jq` incantations myself. Has anyone here been in a similar situation? Which tool / language did you end up exposing to your users?

1. nothrabannosir ◴[28 Oct 25 10:21 UTC] No.45731074[source]▶
crucial jq insight which unlocked the tool for me: it's jsonl, not json.

it's a pipeline operating on a stream of independent json terms. The filter is reapplied to every element from the stream. Streams != lists; the latter are just a data type. `.` always points at the current element of the stream. Functions like `select` operate on separate items of the stream, while `map` operates on individual elements of a list. If you want a `map` over all elements of the stream: that's just what jq is, naturally :)

stream of a single element which is a list:

    echo '[1,2,3,4]' | jq .
    # [1,2,3,4]
unpack the list into a stream of separate elements:

    echo '[1,2,3,4]' | jq '.[]'
    # 1
    # 2
    # 3
    # 4
    echo '[1,2,3,4]' | jq '.[] | .' # same: piping into `.` is a NOP:
only keep elements 2 and 4 from the stream, not from the array--there is no array left after .[] :

    echo '[1,2,3,4]' | jq '.[] | select(. % 2 == 0)'
    # 2
    # 4
keep the array:

    echo '[1,2,3,4]' | jq 'map(. * 2)'
    # [2,4,6,8]
map over individual elements of a stream instead:

    echo '[1,2,3,4]' | jq '.[] | . * 2'
    # 2
    # 4
    # 6
    # 8
    printf '1\n2\n3\n4\n' | jq '. * 2' # same
This is how you can do things like

    printf '{"a":{"b":1}}\n{"a":{"b":2}}\n{"a":{"b":3}}\n' | jq 'select(.a.b % 2 == 0) | .a'
    # {"b": 2}
select creates a nested "scope" for the current element in its parens, but restores the outer scope when it exits.

Hope this helps someone else!