Show HN: JAQT – JavaScript Queries and Transformations | Hacker News Reader

Show HN: JAQT – JavaScript Queries and Transformations

github.com

100 pointsPoefke31 comments

Hi all,

I've made a javascript library to simplify searching/sorting/filtering in arrays of objects. Its inspired by both GraphQL and SQL, but implemented using javascript Proxies. Instead of creating a new language, its all just javascript.

I've made it as part of an experimental database, which uses javascript as the query engine. The normal javascript map/reduce/sort functions are quite difficult to master for junior developers. JAQT is easier to explain, and can still be used in combination with any existing array functions.

Please let me know what you think of the API and its ease of use!

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Wouldn't the query for your example just be

data.filter(d => d.friends.includes("John")).map(d => ({name: d.name+" "+d.lastName}))

Maybe I'm missing the bigger picture, but that doesn't seem so bad

one of the cases something like this is useful for is when you have user configured saved 'filters' - you can simply pass the stored object into the where clause. I agree if you're doing hard-coded queries on arrays of objects, this may not add a lot. That said, a consistent syntax for doing searches and mapping is useful - projects like lodash have that as part of their api too.

This is actually a pretty decent use case for something like this. You could technically convert a user provided filter function to a string to serialize it, then recreate it using the Function() constructor, but that requires adding 'unsafe-eval' to your content security policy [1][2].

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

[2] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

and it requires users to define filter functions, which isn't happening with any users I deal with :)

I liked JAQT API but it is not really good to create a layer on top of already simple functional constructors.

Why is that not good? JavaScript is full of layers of unnecessary abstraction often for completely superficial reasons and sometimes even irrationally applied at great cost in defiance of evidence and simplicity. So, what makes this specific example less good than all the other countless examples of abstractions most JavaScript developers would happily die to defend?

because in the past it didn't have those functional constructors so things like underscore or lodash would be needed but adding a layer as you mentioned. It is not good, for me, to add a dependency for this again. But in the end I have in my utils file a few functions that basically do what JAQT does and I might copy a few more.

Author here, if you are comfortable with filter/map/reduce, than JAQT doesn't provide much benefits, I agree. My target audience is developers who aren't that used to that. I've had much more success with junior developers using JAQT, then trying to get them to use map/reduce.

I like that it mimics SQL queries/filtering which is straightforward.

Typically I use something like JSONPath [1] (basically XPath for JSON) [2] or jq for this but having more options with other syntax and style is helpful.

For streamed JSON like NDJSON [3] there are some nice filtering options [4]

[1] https://en.wikipedia.org/wiki/JSONPath

[2] https://datatracker.ietf.org/doc/html/rfc9535

[3] https://github.com/ndjson/ndjson-spec

[4] https://github.com/mbostock/ndjson-cli?tab=readme-ov-file#fi...

Looks like .net Linq. Many js projects use lodash and variants, how do you compare that?

LINQ is much more sophisticated, translating as much of the query as possible to the target (server) language, like SQL. JAQT is not doing that. lodash, underscore, and others, had a great impact on javascript by introducing lots of functional paradigms. Most of that is now part of javascript itself. JAQT's main purpose is to allow you to filter arrays of objects and create custom objects, just like GraphQL. And be a bit easier to learn than Array.map/reduce/filter.

With JSON, sometimes you just need a fluent, permissive way to query objects that you don't already know a type structure for. This seems useful! I love JSONata for exploring json data, but it's more useful for static analysis than programming.

can a query like that be observable? so updating the array/object would cause the results to update?

AFAICT this library generates "flat" JSON objects. Wouldn't be too hard to implement it such that references to Javascript objects are instead returned, where some sort of callback could be invoked whenever the actual object is modified. I do rather like this "query engine" approach, too. It's a much cleaner interface IMO and doesn't seem to incur too much overhead either....

Dexie supports observable queries, but it operates on IndexedDB rather than plain JS objects: https://dexie.org/docs/liveQuery()#vanilla-js

I don't know if RxJS has run out of fashion, but that would give you observable js using map/filter/reduce etc.

Thanks. Looks really useful.

This is everything i wanted

For the same purpouse I ofter use this https://github.com/calmm-js/partial.lenses

There is another excellent write-up exploring the theory / use-cases for such libraries https://www.inkandswitch.com/cambria/ (and a corresponding library at https://github.com/inkandswitch/cambria-project)

In a similar vein is https://pbeshai.github.io/tidy/ which I've used for 3+ years. It's a really nice lightweight transformer.

I've also used https://github.com/uwdata/arquero once (better performance for large datasets).

any idea what does tidy uses internally? or is it iterating over entire array for every operation?

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