code: function defaults(options, defaultOptions) {
    options || (options = {});
  
    for (var opt in defaultOptions) {
      if (defaultOptions.hasOwnProperty(opt) && !options.hasOwnProperty(opt)) {
        options[opt] = defaultOptions[opt];
      }
    }
  
    return options;
  }
docs: simple function for extending an object with defaults
  @api private