edgarpf / nth-prime Goto Github PK

This is not a real issue. Your code works fine.
Its just, that it could be formatted & simplified.

Ideas:

• format code
• use single method, no real need because of points below
  --> the variable position is actually needed (otherwise not)
• variable position can be included into the for-loop head
• test if argument is actually a integer ?
  --> use Number.isInteger(n)
• test if argument is a positive integer ?

(- generate primes another way to increase efficiency)

Result:

• safety
• readability
• no change in runtime
• Code:

module.exports = function(n) {
  if (!Number.isInteger(n)) {
    throw new Error("The argument must be an integer.");
  }
  if (n <= 0) {
    throw new Error("The number must be a positive integer.");
  }

  return nthPrime(n);
}

function nthPrime(n) {
  // first prime
  if (n == 1) {
    return 2;
  }

  // n-th prime
  for (var i = 3, j = 1; ; i += 2) {
    // increment counter
    if (isPrime(i)) {
      j++;
    }

    // found n-th prime
    if (j == n) {
      return i;
    }
  }
}