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Comment by uDontKnowMe | Hacker News Reader

IMO it would also be really nice to have non-string keys in objects, like:

{ [1, 2]: "a", [3, 4]: "b" }

You realize this would push outside of what JavaScript provides?

    'Welcome to Node.js v15.7.0.
    Type ".help" for more information.
    > { [1, 2]: "a" }
    ({ [1, 2]: "a" })
        ^
    Uncaught SyntaxError: Unexpected token ','

Thar' be dragons! https://stackoverflow.com/questions/32660188/using-array-obj...

it's true JS doesn't support this, and it's also true that any JSON that supported it would therefore no longer be _JavaScript_ object notation.

However, it's equally true that a better language and object notation would support non-string scalar keys.

JavaScript wouldn't be able to consume those resulting objects, so it would be pretty diminished as an alternative to JSON. Object keys are all strings.

Not that I find this idea useful for otherwise limited DTO format, which JSON is, but JS has Map, which may be used for such maps.

Sadly because arrays are not immutable you can't meaningfully use them as Map keys. You'd need a tuple type, which does not currently exist.

I can see why you want non-string scalar keys. In general, I do too. (I'm writing a data language that has them.)

However, I don't think it is useful to prod JSON (or a variant) to go in this direction.

Why not?

JSON is extremely closely linked with JavaScript. Trying to move it in a different direction, in my opinion, would require a lot of effort, without much benefit, and is unlikely to succeed.

JSON is used lots of places JavaScript isn't. It hasn't been closely linked with JavaScript since people realized eval is dangerous.

People are more interested in JSON derivatives like JSON5 or Ion than more complex languages like Dhall in my experience.

All fair points.

Dhall is new to me. Would you tell me more about other configuration languages you seen? I often use TOML myself.

it's usually a pretty bad idea to have a mutable object (the array) as a key. Though I guess if you consider it as a 'tuple' since when in json form it can't be modified I guess it'd be technically possible, though with some heavy caveats.

There’s no concept of mutability in JSON. A JSON parser could give you immutable arrays and maps if it wanted to.

Yes, but json by itself doesn't actually do anything. It'd always be used in context of javascript/python/ etc.. As I said you could interpret it as a tuple or I guess a frozen array for javascript? I don't think there is a native immmutable array in javascript.

If it's a map I'm a bit more unsure how you'd check to find the object (quickly). You're basically getting into the how to store a struct/class as a map key. Either way its a bit more involved than just having json parser return an immutable array and map, and the more I think about it the more edges cases there are.

> I don't think there is a native immmutable array in javascript.

I'm here to tell you that `Object.freeze()` works just fine on arrays.

Nice. Though I don't think that solves the rest of the issues I outlined sadly.

I guess you could have this json+ convert into some custom javascript class that allows arrays/objects as map keys rather than the normal javascript object that only accepts strings as map keys.

> I guess you could have this json+ convert into some custom javascript class that allows arrays/objects as map keys rather than the normal javascript object that only accepts strings as map keys.

Sure - why not? JSON doesn't have to map directly to JavaScript objects.

Why?

One of the uses is mapping values to objects instead of strings, so you don’t have to use ids:

  ob = {...}
  somemap[ob] = value
  // vs
  somemap[ob.id] = value

In languages which allow weak keys in such maps, a garbage collector may even reclaim whole key-value pairs once ob falls out of existence. But to my opinion, in json it is barely useful for a number of reasons. It is more programming technique than data transfer format, and these features (and reference loops) should be encoded at a higher level than json.

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