Code for finding GCD or HCF

Note: GCD and HCF are same GCD: Greatest common divisor HCF: Highest common factor

Using Recursion

function gcd(a, b) {
  if (b === 0) return a;
  return gcd(b, a % b);
}

gcd(15, 20); // 5

Using FOR loop

function gcd(a, b) {
  let hcf = -1;

  for (let i = 1; i <= a && i <= b; i++) {
    if (a % i == 0 && b % i == 0) {
      hcf = i;
    }
  }

  return hcf;
}

gcd(15, 20); // 5

Using WHILE loop

function gcd(a, b) {
  while (a != b) {
    if (a > b) {
      a -= b;
    } else {
      b -= a;
    }
  }

  return a;
}

gcd(15, 20); // 5