Express routes parameter conditions

Question

I have a route on my Express app that looks like this:

app.get('/:id', function (request, response) {
  …
});

The ID will always be a number. However, at the moment this route is matching other things, such as /login.

I think I want two things from this:

to only use this route if the ID is a number, and
only if there isn't a route for that specific paramater already defined (such as the clash with /login).

Can this be done?

score 142 · Accepted Answer · edited Apr 12 '13 at 14:31

142

Expanding on Marius's answer, you can provide the regex AND the parameter name:

app.get('/:id(\\d+)/', function (req, res){
  // req.params.id is now defined here for you
});

edited Apr 12 '13 at 14:31

Fluffy

answered Jun 29 '12 at 10:45

danmactough

Great, but now if I have a route for say `/1` elsewhere, it's still going to call that. Anyway to prevent this? – Jun 29 '12 at 10:56
14

As long as the explicit `/1` route is added first it will take precedence. – JohnnyHK Jun 29 '12 at 11:18
2

You can place the explicit routes first, as JohnnyHK says. You may also be able to define the RegEx to not match the routes you want to skip. – danmactough Jun 29 '12 at 14:51
Order your route handlers in priority order and then use `function(req, res, next)`, calling next() from within any route when your logic knows that it needs to pass control onto the next route handler in line. – awhie29urh2 Apr 18 '13 at 00:07
if you use an alpha-numeric id like Mongo ObjectID you will need to change the regex – Alexander Mills Nov 01 '15 at 23:47
Great! Works for me. Express version `~4.15.3`. I could make two routes with this technique: `/users/online` and `/users/21`, `/users/online` and `/users/:id(\\d+)` respectively. – Green Sep 04 '17 at 05:58
is the id parameter optional in this route? If not, how would I make it optional? I know that '/:id?' makes the id parameter optional but do I still need the question mark and, if so, where would it go? – T. Stoddard Nov 07 '19 at 18:41

Marius Kjeldahl · Answer 2 · 2015-11-14T19:23:20.443

12

app.get(/^(\d+)$/, function (request, response) {
  var id = request.params[0];
  ...
});

edited Nov 14 '15 at 19:23

answered Jun 29 '12 at 08:34

Marius Kjeldahl

score 4 · Answer 3 · answered Dec 29 '12 at 07:23

4

You can use:

// /12345
app.get(/\/([^\/]+)\/?/, function(req, res){
  var id = req.params[0];
  // do something
});

or this:

// /post/12345
app.get(/\/post\/([^\/]+)\/?/, function(req, res){
  var id = req.params[0];
  // do something
});

answered Dec 29 '12 at 07:23

Marco Godínez

3 Answers3