How to adapt JSON.Parser for NaN in Javascript?

I’m trying to adapt JSON.Parse() for NaN.

console.log(JSON.parse('{"n": 1}'));
console.log(JSON.parse('{"n": NaN}'));

1st one is {n:1}.

2nd one has an error which says Unexpected token N in JSON.
And I want to change NaN to 0 like {n: 0}.

I found a resource which create JSON Parser from scratch.https://lihautan.com/json-parser-with-javascript/#implementing-the-parser

It’s good he separates keys and values so that I can check only values if there is NaN and fix it.
But the problem is I have no idea where I can put the NaNParser() and the process. Because the parameter looks coming 1 by 1 character.

If you could give me some advice, it really helps me.
https://codesandbox.io/s/json-parser-with-error-handling-hjwxk?from-embed