code: function expandUrl(url, base) {
      if (!base)
          return url;
      if (url.match(/^(\/|https?:\/\/)/))
          return url;
      if (base.substr(base.length - 1) !== '/') {
          base = base + '/';
      }
      return base + url;
  }
docs: Expands a URL that may or may not be relative to `base`.
  
  @param {string} url
  @param {string} base
  @return {string}