Yup, this is exactly the problem. Currently JSON.parse() will silently truncate large numbers. This behavior made sense when there was only one numeric type in the language, but BigInt opens the door for arbitrary precision integers.
> JSON is agnostic about the semantics of numbers. In any programming language, there can be a variety of number types of various capacities and complements, fixed or floating, binary or decimal. That can make interchange between different programming languages difficult. JSON instead offers only the representation of numbers that humans use: a sequence of digits. All programming languages know how to make sense of digit sequences even if they disagree on internal representations. That is enough to allow interchange
and later more precisely defines a number in a way that does not restrict its maximum size.
> A number is a sequence of decimal digits with no superfluous leading zero. It may have a preceding minus sign (U+002D). It may have a fractional part prefixed by a decimal point (U+002E). It may have an exponent, prefixed by e (U+0065) or E (U+0045) and optionally + (U+002B) or – (U+002D). The digits are the code points U+0030 through U+0039.
http://www.ecma-international.org/publications/files/ECMA-ST...