code: function loadData() {
    var data = fs.readFileSync(__dirname + '/zip_codes.csv', 'utf8');
    var lines = data.split('\r\n');
    var trie = {};
  
    lines.forEach(function(line) {
      var parts = line.split(',');
      var zip = parts[0], city = parts[1], state = parts[2];
      var node = trie;
    
      for (var i = 0; i < zip.length; i++) {
        var num = zip[i];
        var pos = node[num];
        if (pos == null)
          node = node[num] = (i === zip.length - 1) ? [city, state] : {};
        else
          node = node[num];
      }
    });
    
    return trie;
  }
docs: Parses zip_codes.csv and creates a trie for fast lookups