Doing the anagram exercise from exercism.io

anagram.js

var anagram = function(word) {
  return new Anagram(word);
};

function Anagram(word) {
  this.matches = matches;
  
  function matches() {
    possible_anagrams = retrieveAnagrams(arguments);
    return possible_anagrams.filter(function(anagram) {
      return notSameAs(anagram) && normalize(word) === normalize(anagram);
    });
  };

  function retrieveAnagrams(args) {
    if(args[0] instanceof Array) return args[0];
    return [].map.call(args, function(anagram) {
      return anagram;
    });
  }

  function notSameAs(anagram) {
    return word.toLowerCase() !== anagram.toLowerCase();
  }

  function normalize(text) {
    return text.toLowerCase().split("").sort().join("");
  }
}

module.exports = anagram;