Cast a variable based on the data type of another variable

Question

I would like to have a function which casts a variable based on its "reference" type variable. I guess the function would take two parameters cast(x, ref), where x is the variable to cast accordingly to the data type of ref. So for example:

let myVar = cast(3, "helloworld");
console.log(myVar); // "3"

let myNewVar = cast(myVar, 32423n);
console.log(myNewVar); // 3n

Right now, I've only managed to transform numbers to bigints if the ref is a bigint

const cast = (n, ref) => typeof ref === "number" ? n : BigInt(n)

It would be nice to cast a variable to the data type of another variable.