`JSON.parse` actually does give you that option via the `reviver` parameter, which gives you access to the original string of digits (to pass to `BigInt` or the number type of your choosing) – so per this conversation fits the "good parser" criteria.
To be specific (if anyone was curious), you can force BigInt with something like this:
//MAX_SAFE_INTEGER is actually 9007199254740991 which is 16 digits
//you can instead check if exactly 16 and compare size one string digit at a time if absolute precision is desired.
const bigIntReviver = (key, value, context) => typeof value === 'number' && Math.floor(value) === value && context.source.length > 15 ? BigInt(context.source) : value
const jsonWithBigInt = x => JSON.parse(x, bigIntReviver)
Generally, I'd rather throw if a number is unexpectedly too big otherwise you will mess up the types throughout the system (the field may not be monomorphic) and will outright fail if you try to use math functions not available to BigInts.
Sorry yes, i was thinking of the context object with source parameter.
The issue it solves is a big one though, since without it the JSON.parse functionality cannot parse numbers that are larger than 64bit float numbers (f.ex. bigints).
