jacobi symbol for bigints

jacobi.js

function jacobi(a, n) {
  if (n <= 0n) throw new Error('n must be positive integer');
  if (n % 2n === 0n) throw new Error('n must be odd');
  a %= n;
  let result = 1;
  while (a !== 0n) {
    while (a % 2n === 0n) {
      a /= 2n;
      let n_mod_8 = n % 8n;
      if (n_mod_8 === 3n || n_mod_8 === 5n) {
        result = -result
      }
    }
    let _a = a;
    a = n, n = _a;
    if (a % 4n === 3n && n % 4n === 3n) result = -result;
    a %= n;
  }
  if (n === 1n) return result;
  return 0n;
}