JSBI with bigints

[s-cork]

Posting here since it might be useful to someone else, it's something I've used in a project that seems to be working well.
(someone will probably tell me why this is a bad idea 😅 )

It has the benefit of being able to use bigint when it's available and JSBI when it's not.

export const JSBI = window.BigInt !== undefined ? {} : require("jsbi");

if (window.BigInt !== undefined) {
    Object.assign(JSBI, {
        BigInt: window.BigInt,
        toNumber: (x) => Number(x),
        toString: (x) => x.toString(),
        unaryMinus: (x) => -x,
        bitwiseNot: (x) => ~x,
        bitwiseAnd: (x, y) => x & y,
        bitwiseOr: (x, y) => x | y,
        bitwiseXor: (x, y) => x ^ y,
        exponentiate: (x, y) => x ** y, // you may need to adjust this (like i did) if your transpiler changes it to Number.pow
        multiply: (x, y) => x * y,
        divide: (x, y) => x / y,
        remainder: (x, y) => x % y,
        add: (x, y) => x + y,
        subtract: (x, y) => x - y,
        leftShift: (x, y) => x << y,
        signedRightShift: (x, y) => x >> y,
        unsignedRightShift: (x, y) => x >>> y, // will raise TypeError
        lessThan: (x, y) => x < y,
        lessThanOrEqual: (x, y) => x <= y,
        greaterThan: (x, y) => x > y,
        greaterThanOrEqual: (x, y) => x >= y,
        equal: (x, y) => x === y,
        notEqual: (x, y) => x !== y,
    });
}

[jakobkummerow]

It's not a bad idea; very early versions of JSBI did something like this internally.

The biggest issue is the ** operator. As you note, transpilers might eliminate it; that's because without transpilation this code will generate SyntaxErrors on sufficiently old JS engines (IIRC: Node 6, IE11).

So if you don't care about supporting such very old engines, then this solution will probably work just fine for you. Otherwise, JSBI's official conclusion is that using https://github.com/GoogleChromeLabs/babel-plugin-transform-jsbi-to-bigint is more robust, and probably fits many projects' workflows well.

(Aside from that, the good news is that nowadays all major browsers support BigInts (see: https://caniuse.com/bigint), so it's only a question of time until developers can just rely on native BigInts being available. Just a few more years!)