BigInt is finally here in ES2020

> Using JSON.stringify() with any BigInt value will raise a TypeError as BigInt values aren't serialized in JSON by default. However, you can implement your own toJSON method if needed

Sorry, why exactly can’t they also define the json.parse/stringify behavior of bigints? JSON was initially derived from JavaScript, so it seems a bit weird that a new ES standard can’t interoperate with json

> BigInt is a built-in object that provides a way to represent whole numbers larger than 2^53 - 1, which is the largest number JavaScript can reliably represent with the Number primitive and represented by the Number.MAX_SAFE_INTEGER constant.

Isn't this wrong? JavaScript's Number type can represent some integers vastly greater than this. [0] What's special about Number.MAX_SAFE_INTEGER, if I understand correctly, is that it's the smallest integer such that (Number.MAX_SAFE_INTEGER + 1) is not guaranteed to be represented faithfully by the Number type.

Given the topic, I don't think I'm being pedantic.

edit On second thought, I could well be mistaken. The definition of JavaScript's Number type might be such that no guarantees are made about which integers greater than Number.MAX_SAFE_INTEGER can be represented exactly.

edit 2 Nope, Number.MAX_VALUE is defined to be an integer. [0] Which is to say, the largest whole number that can be represented is Number.MAX_VALUE, not Number.MAX_SAFE_INTEGER. Of course, it's not the case that Number is guaranteed to be able to exactly represent all non-negative integers less than Number.MAX_VALUE, but that isn't the same thing. The article appears to get this wrong.

[0] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

I think you misread the sentence. It's not the largest value JS can represent, it's the largest value it can "reliably represent". After 2^53 - 1 you get incorrect results when dealing with integers, making the results not "reliable".

When an integer can be reliably represented, that presumably means that JavaScript's definition of the Number type is such that it guarantees that a given integer can be represented exactly by the Number type. It doesn't mean you can safely do arbitrary integer arithmetic on it and get back another integer, also represented exactly. Trivially, there are no such values.

Every non-negative integer up to and including Number.MAX_SAFE_INTEGER can be represented exactly by the Number type, in any compliant JavaScript implementation. It's also true though that Number.MAX_VALUE is itself defined to be an integer. It's therefore not true to say that Number.MAX_SAFE_INTEGER is the greatest integer that can be exactly represented by JavaScript's Number type.

Instead, Number.MAX_SAFE_INTEGER is the greatest integer such that Number.MAX_SAFE_INTEGER can be represented precisely by the Number type, and all non-negative integers less than Number.MAX_SAFE_INTEGER can be represented exactly by the Number type. (See also my second edit to my earlier post.)

It seems incorrect then that the article states:

> 2^53 - 1, which is the largest number JavaScript can reliably represent with the Number primitive and represented by the Number.MAX_SAFE_INTEGER constant

There's discussion of the term safely represent on the MAX_SAFE_INTEGER page. [0]

[0] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

Ah, now I see it the whole point - "reliably representable" not meaning the same as "safe", gotcha.