Karatsuba multiplication in JS

karatsuba.js

const karatsuba = (x, y, l) => {
  if (l <= 2) {
    return x * y;
  }

  const l_2 = l / 2n;
  const half = 10n ** l_2;

  const a = x / half;
  const b = x % half;
  const c = y / half;
  const d = y % half;

  return (
    10n ** l * karatsuba(a, c, l_2) +
    half * (karatsuba(a, d, l_2) + karatsuba(b, c, l_2)) +
    karatsuba(d, b, l_2)
  );
};

const traditionalMultiplication =
  BigInt("6745896724546734658950865974635261545768459589748632415463257657") *
  BigInt("9345872469823451516517615876937639745346369324563458754923465349");

const karatsubaMultiplication = karatsuba(
  BigInt("6745896724546734658950865974635261545768459589748632415463257657"),
  BigInt("9345872469823451516517615876937639745346369324563458754923465349"),
  64n
);

console.log(karatsubaMultiplication);
console.log(traditionalMultiplication === karatsubaMultiplication);

/*
63046290482213522841036229052622386403907374545967197641214085642152283525360434286859603802055738768753469016012669606898427293n
true
*/