prime-number-check/index.js

Checks if a number is prime or not

//a package created to check if a number is prime
//return true if the number is prime else false
//here number is represented as 'n'
function isPrime(n) {
  //check if n is number and not a string and not an integer
  //if n is not a number or not a integer or less than 2 then return false
  if (typeof n !== "number" || !Number.isInteger(n) || n < 2) {
    return false;
  }

  //check if n is equal to 2, if yes 2 is only even prime number
  if (n === 2) {
    return true;
  }

  //check if n is even number, if yes then n is not a prime number
  if (n % 2 === 0) {
    return false;
  }

  //iterate from 3 to square root of n, incrementing by 2
  for (let i = 3; i <= Math.sqrt(n); i += 2) {
    //check if n is divisible by values of i
    if (n % i === 0) {
      //n is not prime as it is completely divisible
      return false;
    }
  }

  //if n is not completely divisible by values of i till the iteration is complete
  //then n is prime
  return true;
}

//export isPrime function
module.exports = isPrime;