JavaScript Trie Implementation

I've been laying around the house this weekend hacking away at little side projects. Here is one of my tangents. Perhaps someone out there will give this little guy a nice home, maybe a Bag implementation or a drop down list for an auto suggest enabled form field.

The Test (and how to use it)

function testThoughtWorks() { 
  var trie = new byrne.TrieNode(/* root */);
  trie.add('thought');

  assertEquals(1, trie.getWordCount('thought'));
  assertEquals(0, trie.getPrefixCount('thought'));

  trie.add('thoughtworks');

  assertEquals(1, trie.getWordCount('thought'));
  assertEquals(1, trie.getPrefixCount('thought'));
  assertEquals(1, trie.getWordCount('thoughtworks')); 
  assertEquals(0, trie.getPrefixCount('thoughtworks'));
  assertEquals(0, trie.getWordCount('foo'));
  assertEquals(0, trie.getPrefixCount('foo'));
}

The Implementation

byrne = {}; // create the namespace

/**
 * @see http://en.wikipedia.org/wiki/Trie
 * @author Dennis Byrne
 * @constructor 
 */
byrne.TrieNode = function(){
  this.wordCount = 0;
  this.prefixCount = 0;
  this.children = [];
};

byrne.TrieNode.prototype.add = function(word) {
  if(word){
    this.prefixCount++;
    var k = word.charAt(0);
    (this.children[k] || (this.children[k] = new byrne.TrieNode()))
      .add(word.substring(1));
  }else
    this.wordCount++;
};

/**
 * Retrieve the prefix count of the applied argument w/ recursion.
 */
byrne.TrieNode.prototype.getPrefixCount = function(word){
  return word ?
    this.getCount(word, arguments.callee) : this.prefixCount;
};

/**
 * Retrieve the word count of the applied argument w/ recursion.
 */
byrne.TrieNode.prototype.getWordCount = function(word){
  return word ?
    this.getCount(word, arguments.callee) : this.wordCount;
};

/**
 * @private
 */
byrne.TrieNode.prototype.getCount = function(word, method){
  var k = word.charAt(0);
  return this.children[k] ?
    method.call(this.children[k], word.substring(1)) : 0;
};