How to parse bigints when using Response.json() function?

[pspraveenkr]

In many cases, JSON parsing happens indirectly when an application calls Response.json() function after fetching JSON payload from a service using the Fetch API.

Would it be within the scope of this proposal to enhance Response.json() to add support for reviver option?
Or, is the recommendation to use Response.text() and then call JSON.parse directly with a reviver function?

Thank you for advancing this proposal! We at Esri are tracking this proposal as part of adding support for big integers to our ArcGIS Online Cloud platform. Not being able to serialize and de-serialize is a blocker at the moment.

[ljharb]

Response isn’t a thing in the language - it’d be the job of, in this case, HTML to add support for it.

[pspraveenkr]

I will open an issue at https://github.com/whatwg/fetch which looks like the right spot for this question.

Thanks!

[WebReflection]

I just tried:

JSON.parse(JSON.stringify(JSON.rawJSON(12345678901234567890n)), (k, v) => { console.log({ k, v }); return v; })

and there's no way I can get the original 12345678901234567890 value in there ... this is not even a reviver functionality, this is about creating JSON no JS runtime can understand and I start wondering what was the original idea around it ... I understand we can get to not lose big numbers when serializing, but it's not clear at all how are we supposed to also consume such big numbers (and basically nothing else that's interesting) once such serialization happens ... is this an API for foreign PLs and not actually or JS ? 🤔

edit never mind, I've just realized the source is different from the returned value ... how bizarre, I should've seen that coming in the reviver.

[bakkot]

@WebReflection

JSON.parse(
  JSON.stringify(JSON.rawJSON(12345678901234567890n)),
  (k, v, c) => { if (typeof v === 'number') return BigInt(c.source); return v; }
)

[WebReflection]

@bakkot ... not quite:

const reviver = (_, value, context) => (
  context && typeof value === 'number' && String(value) !== context.source ?
    BigInt(context.source) : value
);