function parseString(str) {
  var obj = {};
  var pairs = str.split('&');
  var parts;
  var pair;

  for (var i = 0, len = pairs.length; i < len; ++i) {
    pair = pairs[i];
    parts = pair.split('=');
    obj[decodeURIComponent(parts[0])] = decodeURIComponent(parts[1]);
  }

  return obj;
}
Parse the given x-www-form-urlencoded `str`.

@param {String} str
@return {Object}
@api private