fibonacci function in BQ

fibonacci_fun.sql

CREATE TEMP FUNCTION fibonacci(n INT64)
RETURNS INT64
LANGUAGE js AS
"""
  var numbers = [0, 1]
  while (n > 1) {
    var new_num = numbers[0] + numbers[1];
    numbers.shift();
    numbers.push(new_num);
    n -= 1;
  }
  return numbers[n];
""";