We wrote something quite similar for Bouygues Telecom and based it on an ANTLR grammar [2].

It offers nested filtering out of the box. All feature-packed in a lightweight package.

[1]: https://github.com/bouyguestelecom/spl [2]: https://github.com/BouyguesTelecom/SPL/blob/main/src/antlr/S...

The README is so good; visual demonstration, documentation, examples, proper Markdown formatting.. Love it.

I'm always asking myself, why there is no language-independent standard for this to translate into SQL / LIST querying or processing and why this is almost never done in a kind of lisp-ish style to have a fast, compact, simple and easy parser...

  (OR 
    (IN id (list 1 2 3)) 
    (LTE createDate "2025-08-27")
  )

  WHERE id IN (1,2,3) OR createDate <= '2025-08-27'

I see a mismatch between the library API `filter` vs the supported operator `| SORT rating desc"`. You could use the API to your advantage by separating concerns: add a new `.sort("fieldName")` method.

``` const recentGoodMovies = filterql .filter(movies, "year >= 2008") .sort("rating") .desc()

```

If adding helper methods for semantics and clarity is not the intent of the library, then I'd rename the `filter` method since it doesn't communicate the intention clearly.

The function executes a full pipeline filter expression + `|` operations like `SORT` and `LIMIT` (not just a predicate filter). So for instance naming it to `query` will match your README terminology and grammar (`query := filter | operation*`)

I myself made a simple query language out of necessity. My key-value CRDT store [1] needed some syntax for basic queries. It was strictly minimalistic, like {type:fruit} would produce [{type:fruit name:banana}...] and so on. When I think how to evolve it I lean towards adding lisp-like expression support. Cause I have a small lisp readily available.

I wonder if there is a good birds-eye FAQ/HOWTO/overview of all the existing (families) of query languages. Just to systematize Datalog, GraphQL, SQL, there are tons of them.

[1]: https://github.com/gritzko/go-rdx

I recently experimented with something like this and ended up going with MongoDB style queries (and field:operator:value syntax for a CLI wrapper)[1] as they are very powerful for nested/array operations and easy to parse everywhere but WAY more verbose than the syntax you chose for filterql! which also seems easy to understand for less technical folks. Love the project, do you plan on supporting nested values?

[1]: https://github.com/nicolaspasqualis/go-fq

Any plans on this supporting JSONSchema? Seeing as most/all popular TypeScript validation libraries, which will likely be used to define the shape of the data, support converting to JSONSchema now?

I like it! It’s nice offering a little DSL in various spaces. Curious where you’re plugging it in?

Any intended support for collections/sets? In JQL is do ‘“foo” not in (“evil”, “silly”)’ or similar matchers over sets, like if tags are on a ticket or if tickets an in an N states

It seems nice. However is there any way to query arrays within the datastructure itself? Or go deeper in the hierarchy, such as "model.cost"?

why a dsl when you could do ql.filter<Movies>(movies).where('y', '>=', 2008) or even just use kysely with a plugin

is there some thing like this in python?

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