code: function getDirective (options, name) {
    if (!options[name]) {
      return null;
    }
  
    if (typeof options[name] === 'string') {
      return name + ' ' + options[name];
    }
  
    if (Array.isArray(options[name])) {
      let result = name + ' ';
      options[name].forEach(value => {
        result += value + ' ';
      });
      return result;
    }
  
    return null;
  }
docs: Helper function to compile one directive. handles strings and arrays.
  
  @param options
  all options
  @param name
  name of the one to compile
  @returns compilation of named option