Find a collection of prime numbers between a range. I began with the primeNumbers function and wrote it the way I'd want to use it; go through a range and call prime() on each number. So that meant I had to create a prime() method for all Numbers using their prototype property. This lead me to research what rules define a number to be prime. The…

primeNumbers.js

var primeNumbers = function(from, to) {
  var primes = [];
  for(var i = from; i <= to; i++){
    if(i.prime()){
      primes.push(i);
    }
  }
  return primes;
};

Number.prototype.prime = function(){
  if(this.even() && this !== 2 ||
     this.sumOfDigitsDivByThree() && this !== 3 ||
     this.lastTwoDigitsDivByFour() ||
     this.lastDigitDivByFive() && this !== 5){
    return false;
  } else {
    return true;
  }
};

Number.prototype.even = function(){
  if(this % 2 === 0){return true;}
};

Number.prototype.sumOfDigitsDivByThree = function(){
  var sum = 0;
  var digits = String(this).split('');
  for(var i = 0, len = digits.length; i < len; i++){
    sum += Number(digits[i]);
  }
  sum % 3 === 0 ? true : false;
};

Number.prototype.lastTwoDigitsDivByFour = function(){
  var number = '';
  var digits = String(this).split('');
  var len = digits.length;
  if(digits.length >= 2){
    number += digits[len - 2];
    number += digits[len - 1];
    Number(number) % 4 === 0 ? true : false;
  } else {
    return false
  }
};

Number.prototype.lastDigitDivByFive = function(){
  var digits = String(this).split('');
  var len = digits.length;
  Number(digits[len - 1]) === 0 || Number(digits[len - 1]) === 5 ? true : false;
};