code: function(breadcrumbs) {
      // known breadcrumb properties with urls
      // TODO: also consider arbitrary prop values that start with (https?)?://
      var urlProps = ['to', 'from', 'url'],
        urlProp,
        crumb,
        data;
  
      for (var i = 0; i < breadcrumbs.values.length; ++i) {
        crumb = breadcrumbs.values[i];
        if (
          !crumb.hasOwnProperty('data') ||
          !isObject(crumb.data) ||
          objectFrozen(crumb.data)
        )
          continue;
  
        data = objectMerge({}, crumb.data);
        for (var j = 0; j < urlProps.length; ++j) {
          urlProp = urlProps[j];
          if (data.hasOwnProperty(urlProp) && data[urlProp]) {
            data[urlProp] = truncate(data[urlProp], this._globalOptions.maxUrlLength);
          }
        }
        breadcrumbs.values[i].data = data;
      }
    }
docs: Truncate breadcrumb values (right now just URLs)