Euler Problem #20 in JS

e20.js

// factorial
f = (n) => {
  n = BigInt(n);
  return (n>1) ? n * f(n-1n) : n;
}

// sum of digits in the number
s = (n) => {
  return n.toString().split("")
          .map(x => parseInt(x))
          .reduce((a, b) => a+b);
}

console.log(s(f(100)));