Passing error message to template through redirect in Express/Node.js

Question

In my Node.js application, I have a function (routed by Express) which presents a form to the user:

app.get('/register', function (req, res) {
  res.render('form');
});

I have another function, routed to the same URL, but which handles POST requests, which receives the data submitted by the previous form. If the form does not validate, it redirects the user back to the form; otherwise, it does what should be done:

app.post('/register', function (req, res) {
  if (validate(req.registerForm)) return res.redirect('back');
  persistStuff(req.registerForm, function (err, data) {
    // Do error verification etc.
    res.redirect('back')
  });
});

What I want to do is to send a error message to be presented, in the line:

if (validate(req.registerForm)) return res.redirect('back');

To write something like

if (validate(req.registerForm)) return res.render('form', {msg:'invalid'});

is unacceptable because I want to follow the POST-REDIRECT-GET pattern. I could do something like

if (validate(req.registerForm)) return res.redirect('/register?msg=invalid');

but it would hardcode an URL in my code and I'd prefer to avoid it. Is there another way to do it?

stackoverflow.com/questions/5555053/…

chovy
– chovy

2012-09-22 05:12:17 +00:00
Commented Sep 22, 2012 at 5:12 — chovy
– chovy, Commented Sep 22, 2012 at 5:12

Dominic Barnes · Accepted Answer · 2011-08-16 15:03:48Z

8

You need to use flash notifications, and it is built into express.

You'll add a message like so: req.flash("error", "Invalid form...");

You'll need a dynamic handler to add the messages to your rendered template, or you can check out the ones TJ has made for express. (express-messages)

answered Aug 16, 2011 at 15:03

Dominic Barnes

28.5k8 gold badges69 silver badges91 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

ingrid Over a year ago

flash doesn't work in node 4.0 or with templates like mustache.

gadu · Accepted Answer · 2013-11-14 09:51:15Z

3

You could simply have it redirect as res.redirect('..?error=1')

the ? tag tells the browser that it is a set of optional parameters and the .. is just a pathname relative recall (like calling cd .. on terminal to move back one directory) and you're browser will direct to the appropriate page with that tag at the end: http://.....?error=1

then you can simply pull the error on the appropriate page by doing a:

if (req.param("error" == 1)) { // do stuff bassed off that error match };

you can hardcode in several different error values and have it respond appropriately depending on what error occurred

edited Nov 14, 2013 at 9:51

answered Nov 14, 2013 at 9:42

gadu

1,8261 gold badge18 silver badges32 bronze badges

2 Comments

brandizzi Over a year ago

Thanks for the alternative, but why or when would it be better than using flash notifications?

gadu Over a year ago

Oh wow, didn't notice that you had even suggested this yourself on the bottom of your question - don't think there are any obvious benefits really; it's a little simpler to implement and errors are a bit more visible/trackable since they are on the URL but they should accomplish the same thing. If your {do something} is a little more involved than just displaying something it's probably a little unsafe to handle it this way since users can exploit it by typing error messages themselves on the URL - but otherwise just more straightforward

Collectives™ on Stack Overflow

Passing error message to template through redirect in Express/Node.js

2 Answers 2

1 Comment

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related