It seems like Array.prototype.sort() is broken with BigInt
This works
const big = [1n, 2n, 3n, 4n];
big.sort();
console.log(big);
// expected output: Array [1n, 2n, 3n, 4n]
But this doesn't :(
const big = [1n, 2n, 3n, 4n];
big.sort((a,b)=>a-b);
console.log(big);
//Error: Cannot convert a BigInt value to a number
or am i doing something wrong?
JavaScript sort method requires a function as a parameter that can compare two elements of the array and return either a positive number, or a negative number or zero. Number is the keyword here.
BigInt operations like addition and subtraction returns BigInt type and not a Number type. And that's why the error you are getting.
So, Something like this should do the job
const big = [1n, 2n, 3n, 4n];
big.sort((a ,b) => {
if(a > b) {
return 1;
} else if (a < b){
return -1;
} else {
return 0;
}
});
console.log(big);
Interestingly, MDN document that I linked to previously, also suggests how to sort an array of BigInts, and it is concise:
Copying the whole section here for posterity:
const mixed = [4n, 6, -12n, 10, 4, 0, 0n]
// ↪ [4n, 6, -12n, 10, 4, 0, 0n]
mixed.sort() // default sorting behavior
// ↪ [ -12n, 0, 0n, 10, 4n, 4, 6 ]
mixed.sort((a, b) => a - b)
// won't work since subtraction will not work with mixed types
// TypeError: can't convert BigInt to number
// sort with an appropriate numeric comparator
mixed.sort((a, b) => (a < b) ? -1 : ((a > b) ? 1 : 0))
// ↪ [ -12n, 0, 0n, 4n, 4, 6, 10 ]
a === b
2n before another 2n or after. Updated the answer, as document says sort should return positive, zero, or negative number.The reason is that a - b in the sort callback function will return a BigInt data type, while sort expects it to return something that is (or can coerce to) a Number data type.
So you can use a > b || -(a < b) as callback expression:
const big = [10n, 9n, 8n, 7n];
big.sort((a, b) => a > b || -(a < b));
console.log(big + ""); // 7,8,9,10Note that the first version (without sort callback) does not work in general, because then sort will compare the elements as strings. It is clear that this can yield results that are not numerically sorted:
const big = [10n, 9n, 8n, 7n];
big.sort(); // string-based sort
console.log(big + ""); // 10,7,8,9 is wrongThis might appear to be broken at first but its not, the problem is definition of the compare function is always expecting a return value of -1, 0, 1 and it has no reason to expect bigint of -1 0 1 cause they all are in range of normal int.. so this should solve
big.sort((a,b)=>a<b?-1:(a>b?1:0));
BigIntis handled differently from typical numerical values. You may need to use a separate library that makes working with these types of values much easier to properly subtract the two. I haven't worked withBigIntbefore, but from my limited understanding, that might be the root of the problem.Number(a-b)but not sure if it's the correct way to handle it. It converts the BigInt to number. If the difference is more thanNumber.MAX_SAFE_INTEGER(2^53 - 1), it will not work