express-params-handler/index.js

Express.js params handler

module.exports = function (handler) {
  if (!(handler instanceof Function || handler instanceof RegExp))
    throw new Error('Unsupported param handler. Either function or Regexp expected');

  return function (req, _res, next, _val, name) {
    const handlerValue = req.params[name];

    if (handler instanceof Function) {
      const newVal = handler(handlerValue);
      if (!newVal) return next('route'); // bypass current route
      req.params[name] = newVal;
    } else if (handler instanceof RegExp) {
      if (!handler.test(handlerValue)) return next('route'); // bypass current route
    } else {
      throw new Error('Should not reach here');
    }

    return next();
  };
};