Detect if a given word is prime according to their letter positions in alphabet.

isprime.js

var alphabet = [
  'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 
  'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 
  'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
];

// get char position in array
function stringToNumber (string) {
  var number = 0;
    
  for ( var i = 0, l = string.length; i < l; i++ ) {
        
    var indexOfChar = alphabet.indexOf(string[i]) + 1;
        
    number = number + indexOfChar;

  }
    
  return number;
}

// detect if a given number is prime
function isPrime (word, number) {
  console.log('Valor: ' + number);
    
  var result;
    
  if (number === 1) {
    // 1 will never be prime
    result = false;
        
  } else if (number === 2) {
    // 2 is the only even number to be prime
    result = true;
        
  } else { // if number is not 1 or 2....
        
    // test if it is even
    if ( number % 2 === 0 ) {
            
      // number can't be divisible by any other number unless 1 or itself
      // the only even number is 2
      result = false;
            
    } else {
      // loop start at 2 and ends at "number - 1"
      // We do this trick because every number can be divided by 1 and itself
      for (var i = 2; i < number; i++) {
                
        // number can't be divisible by any other number unless 1 or itself
        if ( number % i === 0 ) {
                  
          result = false;
                    
          // exit loop
          break;
                
        } else {
          // aha, we got a prime number
          result = true;
        }
                
      }
            
    }

  }
    
  if (result) {
    console.log(word + ' IS a prime word');
  } else {
    console.log(word + ' IS NOT a prime word');
  }
  
}

var wordToTest = 'Fernando';

// returns 103
var number = stringToNumber(wordToTest);

// arguments('Fernando', 103)
isPrime(wordToTest, number);