code: function normalize(path) {
    if (!path) {
      return '/';
    }
    if (path[0] !== '/') {
      path = '/' + path;
    }
    if (path[path.length - 1] !== '/') {
      path = path + '/';
    }
    return path;
  }
docs: Normalize path
  
  @param {String} path
  @returns {String}