Return true if the string in the first element of the array contains all of the letters of the string in the second element of the array.

bonfire-mutations.js

// Bonfire: Mutations
// Author: @joepichardo
// Challenge: http://www.freecodecamp.com/challenges/bonfire-mutations
// Learn to Code at Free Code Camp (www.freecodecamp.com)

function mutation(arr) {
  /*
    compareChars is made into an array of lowerCase letters
    compareToString is the string to compare the letters with and it is lowercased
    we make containsChars true at first, until function tells us otherwise
  */
  var compareChars = arr[1].toString().toLowerCase().split("");
  var compareToString = arr[0].toString().toLowerCase();
  var containsChars = true;
  
  /*
  we go through the letters we need to compare, 
  hence the arr[1] string length comparison
  if letter is not in the string we are comparing 
  it to -1 is returned, which then returns a false value
  */
  for(var i = 0; i < arr[1].toString().length; i++){
    if(compareToString.indexOf(compareChars[i]) == -1){
      containsChars = false;
    } 
  }
  return containsChars ;
}

mutation(["hello", "hey"]);