Consider mapping BigInt to String for JSON stringify

[Eccenux]

Description

Current implementation (in Chrome) throws on BigInt strinigify:

JSON.stringify({a:123n})

VM97:1 Uncaught TypeError: Do not know how to serialize a BigInt
    at JSON.stringify (<anonymous>)

I think it would make sens if a string mapping would be provided (similar to Date mapping provided with date.toISOString() method).

Example

This is an example and that currently works:

JSON.stringify({a:123n, b:{c:12n}}, function(key, value){
	if (typeof value === 'bigint') {
		return value.toString() + "n";
	} else {
		return value;
	}
});

It produces a valid(!) JSON:

"{"a":"123n","b":{"c":"12n"}}"

A parser could then be provided to recognize and parse BigInt if required.

[bakkot]

See discussion in #24.

I don't think outputting a string is a good default behavior here, since it would not (and cannot) parse back to a BigInt. You can of course trivially make stringify do the thing you want already, as you've pointed out.

[Eccenux]

Oh. Didn't realize implementing toJSON on BigInt is already supported. Never mind then :-). And thanks.

[kaizhu256]

@bakkot, there's prior art for allowing JSON.stringify (to string mapping), but not JSON.parse with Date-objects.

figuring out how to idiot-proof serializing and passing-around 64bit integers to-and-fro
browser <-> server <-> databases
is a big enough industry-painpoint in my mind, that BigInt should try to address it in some form.

even without JSON.parse, having a standardized JSON.stringify for BigInt to plain-strings, would still be tremendously helpful in industry by having everyone agree to a common serialization format.