Storing IP addresses in a tree using a lightweight defaultdict implementation.

gistfile1.js

function defaultdict(default) {
  this._default = default;
};
defaultdict.prototype = {
  get: function(key) {
    if (!key in this) { this[key] = this._default(key); }
    return this[key];
  }
}

addrs = defaultdict(function() { 
          return defaultdict(function() {
            return defaultdict(function() {
              return [];
            });
          });
        });

addrs.get(ip[0]).get(ip[1]).get(ip[2]).push(text);