Calling next inside a helper-function? - node.js

Question

I'm trying to setup a simple system for rendering user-input-errors and stopping propogation in express, this is what I've got so far:
routingFunction= (req, res, next) {
//setting up a test in express-validator
var test = req.assert('access_token', 'required').notEmpty();
isValid(test, next);
//non error stuff
}
isValid = (tests, next) => {
//some more code here, that checks if any errors were found and save tem to the array errors.
if(errors.length > 0){
return next(new Error());
}
};
//a middleware that catches errors:
app.use((err, req, res, next) => {
res.json('error').end();
});
My problem with this is that it doesn't stop the propagation when I'm calling Next(new Error());, I could return true/false from isValid and then return next(new Error()), but that would add a lot of bloat to my controllers, is there some better way to do it from within the helper function?

Answer 1

In main route file, e.g. routes/index.js
// Set of func(req, res, next)
let v = require('validator'); // middleware-validators
let user = require('user'); // routes for user
...
app.get('/smth-route-of-user', v.isTokenSet, v.isEmail, ..., user.get)
In middlewares/validator.js
let v = require('validator-func-list');
...
exports.isTokenSet = function (req, res, next) {
if (v.isValid(req.body.token))
next(); // Forwarding to next middleware. In our route next() called v.isEmail
else
next(new Error('Token is empty')); // Stop route chain and call error-middleware;
}
exports.isEmail = function (req, res, next) {
...
You can join validators to one, e.g. checkUser(), and use only one in route.
In middlewares/errorHandler.js
module.exports = function (err, req, res, next) {
let msg = err.message; // Here we see 'Token is empty';
if (req.xhr)
res.json(msg);
else
res.render('error_page.html', {message: msg, ...});
// Here we can call next(err) to forwarding error to next errorHandler. In example below it was errorHandler2.
}
In app.js don't forget to attach error-middleware to application.
app.use(require('middlewares/errorHandler'));
app.use(require('middlewares/errorHandler2'));
If you need collect errors then validator must push error to req.errors (or another field as you want) and call next() without error. In render middleware you simple check req.errors.length and show normal or error page.

Answer 2

Code after isValid(test, next); always execute. Code below block it, but imho is dirty.
routingFunction = (req, res, next) {
var test = req.assert('access_token', 'required').notEmpty();
if (!isValid(test, next))
return; // callback called by isValid. It's dust.
//non error stuff
...
next(); // callback must be called
}
isValid = (tests, next) => {
if(errors.length > 0){
next(new Error());
return false;
}
return true;
};
More better use like this
routingFunction = (req, res, next) {
var test = req.assert('access_token', 'required').notEmpty();
if (!isValid(test))
return next (new Error('error description'));
//non error stuff
...
next();
}