http://www.freecodecamp.com/dbess1 's solution for Bonfire: Mutations

bonfire-mutations.js

// Bonfire: Mutations
// Author: @dbess1
// Challenge: http://www.freecodecamp.com/challenges/bonfire-mutations
// Learn to Code at Free Code Camp (www.freecodecamp.com)

function mutation(arr) {
  
 var stringToArray1 = arr[0].toLowerCase().split(""); //h,e,l,l,o
 var stringToArray2 = arr[1].toLowerCase().split(""); //h,e,y
  
  
 for (i = 0; i < stringToArray2.length; i++) {
    if (stringToArray1.indexOf(stringToArray2[i]) == -1) //if arr[0] and arr[1] do not equal
      return false;                                      //you get -1 accorrding to MDN
    
  }
  
      return true;

  
}

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