_match = function _match(input, pattern) {
        if (typeof pattern === "string") {
          if (input.indexOf(pattern) !== 0) {
            return null;
          }

          return pattern;
        } else {
          var match = input.match(pattern);

          if (!match) {
            return null;
          }

          return match[0];
        }
      }
@type {{(input: string, pattern: string | RegExp): string | string[] | null;}}