simple querystring parser in javascript using the DOM

query_string_parser.js

var QueryStringParser;

QueryStringParser = (function() {

  function QueryStringParser(url) {
    var parser, _that;
    this.query_params = {};
    if (!document || !document.createElement) {
      throw 'This needs to be run in an HTML context with a document.';
    }
    parser = document.createElement('a');
    parser.href = url;
    this.url = url;
    if (parser.origin) {
      this.origin = parser.origin;
    } else {
      this.origin = [parser.protocol, '//', parser.host].join('');
    }
    this.protocol = parser.protocol;
    this.pathname = parser.pathname;
    this.hash = parser.hash;
    _that = this;
    _.each(parser.search.substr(1).split('&'), function(params) {
      var kv;
      kv = params.split('=');
      return _that.query_params[kv[0]] = kv[1];
    });
  }

  QueryStringParser.prototype.toString = function() {
    var bits, q;
    q = _.compact(_.map(this.query_params, function(v, k) {
      if ((typeof v !== 'undefined') && (v !== null)) {
        return [k, v].join('=');
      }
    })).join('&');
    bits = [this.origin, this.pathname].join('');
    if (q) {
      bits += "?" + q;
    }
    if (this.hash) {
      bits += this.hash;
    }
    return bits;
  };

  return QueryStringParser;

})();