Allow specifying JSON stringifier

[brandon-leapyear]

It would be great to be able to override the JSON.stringify call in res.json(), to use json-bigint to serialize JSON objects

[dougwilson]

It looks like you opened a PR on this feature request before we could understand more. In order to ensure a conversation does not get fragmented, we will close this issue or the PR. Which one would you prefer us to keep open?

[brandon-leapyear]

You can close the PR until discussion here has concluded. Alternatively, I can change the PR to draft mode?

[dougwilson]

As long as draft mode prevents others from accidentally commenting on the pr that is fine 👍

I saw your issue open when I was running errands (and still am), but was going to ask what this helps enable that the json replacer setting cannot do. I looked at the module you referenced but couldn't see it documented what the stringify actually did (but I am mobile, so could have missed it).

I know javascript has BigInt and JSON.stringify works with those no problems. Can you show what object you are trying to stringify that gives the wrong output?

[brandon-leapyear]

Technically speaking, people can still comment on closed PRs. I turned the PR into draft mode and added a comment to discuss on the issue page until further notice.

I know javascript has BigInt and JSON.stringify works with those no problems.

This isn't true. Neither JSON.parse nor JSON.stringify have BigInt support, which is a major source of frustration for me right now :)

> 123948124923742397432n
123948124923742397432n

> JSON.parse('{"x":123948124923742397432}')
{ x: 123948124923742400000 }

> JSON.stringify(123948124923742397432n)
Uncaught TypeError: Do not know how to serialize a BigInt
    at JSON.stringify (<anonymous>)

For now, we're using the json-bigint library in order to have BigInt support when serializing/deserializing JSON. That library has two options: either use the native BigInt or use the bignumber.js library. For other reasons that I won't go into, we're using the bignumber.js implementation, whose default JSON representation is a string

> const BigNumber = require('bignumber.js')
> let x = new BigNumber('123948124923742397432')
> JSON.stringify({ x })
'{"x":"123948124923742397432"}'

In order to get it to serialize as a number, you have to use json-bigint's function

> const JSONbig = require('json-bigint')
> JSONbig.stringify({ x })
'{"x":123948124923742397432}'

[dougwilson]

Ah, gotcha. So it would seem like using the json replacer option would work great for you use case. Is there something wrong with that setting that is keeping it from working for you?

[brandon-leapyear]

I don't think that would work. The problem is if the replacer function converted a BigInt/BigNumber into a number, it would lose the precision and get rounded off. But if the replacer function returned the BigInt/BigNumber as a string (to keep the precision), it would serialize it as a string, not as a JSON number.

I don't think there's a way to use the replacer function to return a string and tell JSON.stringify "hey trust me this is a JSON number, interpolate it directly without quotes".

[brandon-leapyear]

@dougwilson Any update on this?

[davidgoli]

@dougwilson I think @brandon-leapyear makes a good case for why the json replacer function isn't adequate. I too think merging his PR would add powerful capabilities to Express. Any further thoughts?

[enyoghasim]

yeah @dougwilson i also think that @brandon-leapyear PR will help express

[EdOlson-Morgan]

@dougwilson I'm having to work around this issue as well, so agree that merging this PR would improve Express overall. Thanks @brandon-leapyear for taking the time with the fix.

[andyfaizan]

Hey people. Any updates on this? @brandon-leapyear 's PR hasn't been merged yet

[juanfabrega]

Hi -- wondering if there are any updates on this, as I'm struggling with the same at the moment.

@brandon-leapyear or others on the thread, would you mind sharing any current workarounds you have for this problem?

[brandon-leapyear]

I believe the current workaround is to not use res.json, but manually run JSONbig.stringify. We have a custom middleware in NestJS that does this automatically.

On Sat, Apr 23, 2022, 4:29 AM juanfabrega @.***> wrote:

Hi -- wondering if there are any updates on this, as I'm struggling with the same at the moment.

@brandon-leapyear https://github.com/brandon-leapyear or others on the thread, would you mind sharing any current workarounds you have for this problem?

— Reply to this email directly, view it on GitHub https://github.com/expressjs/express/issues/4453#issuecomment-1107456201, or unsubscribe https://github.com/notifications/unsubscribe-auth/AGUC75MGZEE6E4KGOIG3S5TVGPNKHANCNFSM4TIBOZRA . You are receiving this because you were mentioned.Message ID: @.***>

[juanfabrega]

For anybody else looking at this issue, my temporary solution was to use the json-bigint library and just override the JSON methods for my whole app. This may be too drastic for some but with the codebase I have, it does the job and I have no qualms about it since it is transparent otherwise.

I just put this code at the top of my app.ts

import JSONBig from 'json-bigint';


// DANGEROUSLY override JSON prototype methods to handle big ints.
JSON.parse = JSONBig.parse;
JSON.stringify = JSONBig.stringify;

[rohanrajpal]

I believe the current workaround is to not use res.json, but manually run JSONbig.stringify. We have a custom middleware in NestJS that does this automatically. … On Sat, Apr 23, 2022, 4:29 AM juanfabrega @.> wrote: Hi -- wondering if there are any updates on this, as I'm struggling with the same at the moment. @brandon-leapyear https://github.com/brandon-leapyear or others on the thread, would you mind sharing any current workarounds you have for this problem? — Reply to this email directly, view it on GitHub <#4453 (comment)>, or unsubscribe https://github.com/notifications/unsubscribe-auth/AGUC75MGZEE6E4KGOIG3S5TVGPNKHANCNFSM4TIBOZRA . You are receiving this because you were mentioned.Message ID: @.>

Hey, I'm also figuring out a way to stringify BigInt using middleware. From the docs I understand one has to implement a middleware this way:

import { Request, Response, NextFunction } from 'express';

export function logger(req: Request, res: Response, next: NextFunction) {
  console.log(`Request...`);
  next();
};

So I guess in your custom middleware, you must have modified the res object and manually stringified the BigInt values? Or is it a little more complex to implement, if you can share a code snippet, it would be super helpful!