如何按路由将参数传递给通用Express中间件功能？

Question

I've written a generic validation function that takes an object as the first parameter with a property required (amongst others) that is an array of strings. It is used to test incoming front end data against any keys found in required . Here's a mockup of how it looks - using underscore to check isEmpty :

validator.js

function validateRequest(options, req, done) {
  const { body } = req;
  const { required } = options;
  const errors = {};

  if (required && required.length) {
    required.forEach(key => {
      const value = `${body[key]}`;

      if (_.isEmpty(value)) {
        errors[key] = 'This field is required';
      }
    });
  }

  if (_.isEmpty(errors)) done({ success: true });
  else done({ success: false, errors });
}

And I currently use it as such:

routes/auth.js

router.post('/login', (req, res, next) => {
  validator.validateRequest({
    required: ['identifier', 'password']
  }, req, result => {
    if (!result.success) return res.status(400).send(result);
    next();
  });
}, auth.login);

I'd like to be able to use it in a cleaner fashion, something more like:

router.post('/login', validator.validateRequest({
  required: ['identifier', 'password']
}), auth.login);

I'd rather not use app.use because it involves me having to worry about always positioning it in the proper hierarchy of the route files and is not scalable in the sense I need it to be. I also have other parameters being passed as options , validating input as numeric, correct zip codes, etc. so the function above is much more in-depth than the example. Is there a way for me to use something like this on a route-by-route basis? There's gotta be a way for my middleware functions to intercept (req, res, next) without having to write it out each time.. right?

Answer 1

The answer was to use a higher order function returning a function that takes (req, res, next) as parameters like this:

validator.js

function validateRequest(options) {
  return (req, res, next) => {
    const { body } = req;
    const { required } = options;
    const errors = {};

    if (required && required.length) {
      required.forEach(key => {
        const value = `${body[key]}`;

        if (_.isEmpty(value)) {
          errors[key] = 'This field is required';
        }
      });
    }

    if (!_.isEmpty(errors)) {
      res.send({ success: false, errors });
    } else {
      next();
    }
  }
}

then it can be used like so:

routes/auth.js

router.post('/login', validateRequest({
  required: ['identifier', 'password']
}), auth.login);