express-subdomain
Is simply express middleware. In the examples below I am using Express v4.x.
Install
With npm, saving it as a dependency.
npm i express-subdomain --save
Simple usage
Let's say you want to provide a RESTful API via the url http://api.example.com
Express boilerplate code:
var subdomain = require('express-subdomain');
var express = require('express');
var app = express();
// *** Code examples below go here! ***
// example.com
app.get('/', function(req, res) {
res.send('Homepage');
});
API Router
var router = express.Router();
//api specific routes
router.get('/', function(req, res) {
res.send('Welcome to our API!');
});
router.get('/users', function(req, res) {
res.json([
{ name: "Brian" }
]);
});
Now register the subdomain middleware:
app.use(subdomain('api', router));
app.listen(3000);
The API is alive:
http://api.example.com/
--> "Welcome to our API!"
http://api.example.com/users
--> "[{"name":"Brian"}]"
Multi-level Subdomains
app.use(subdomain('v1.api', router)); //using the same router
http://v1.api.example.com/
--> "Welcome to our API!"
http://v1.api.example.com/users
--> "[{"name":"Brian"}]"
Wildcards
Say you wanted to ensure that the user has an API key before getting access to it... and this is across all versions.
Note: In the example below, the passed function to subdomain can be just a pure piece of middleware.
var checkUser = subdomain('*.api', function(req, res, next) {
if(!req.session.user.valid) {
return res.send('Permission denied.');
}
next();
});
app.use(checkUser);
This can be used in tandem with the examples above.
Note: The order in which the calls to app.use() is very important. Read more about it here.
app.use(checkUser);
app.use(subdomain('v1.api', router));
Divide and Conquer
The subdomains can also be chained, for example to achieve the same behaviour as above:
var router = express.Router(); //main api router
var v1Routes = express.Router();
var v2Routes = express.Router();
v1Routes.get('/', function(req, res) {
res.send('API - version 1');
});
v2Routes.get('/', function(req, res) {
res.send('API - version 2');
});
var checkUser = function(req, res, next) {
if(!req.session.user.valid) {
return res.send('Permission denied.');
}
next();
};
//the api middleware flow
router.use(checkUser);
router.use(subdomain('*.v1', v1Routes));
router.use(subdomain('*.v2', v2Routes));
//basic routing..
router.get('/', function(req, res) {
res.send('Welcome to the API!');
});
//attach the api
app.use(subdomain('api', router));
app.listen(3000);
Invalid user
http://api.example.com/
--> Permission denied.
Valid user
http://api.example.com/
--> Welcome to the API!
http://v1.api.example.com/
--> API - version 1
http://abc.v1.api.example.com/
--> API - version 1
http://v2.api.example.com/
--> API - version 2
http://abc.v2.api.example.com/
--> API - version 2
Developing Locally
If you plan to use this middleware while developing locally, you'll have to ensure that your subdomain is listed in your hosts file.
On Linux or OSX, add your subdomain to /etc/hosts
:
127.0.0.1 myapp.dev
127.0.0.1 subdomain.myapp.dev
You may not have write permissions on your hosts file, in which case you can grant them:
$ sudo chmod a+rw /etc/hosts
Note: Express parses the request URL for a top level domain, so developing locally without one won't be possible because Express will treat the subdomain as the domain, and the actual domain as a TLD.
Windows
On Windows 7 and 8, the hosts file path is %systemroot%\system32\drivers\etc
.
Gotchas
Multilevel TLD's, such as .co.uk
you have to pass api.example
as the subdomain:
app.use(subdomain('api.example', router));
See #17 for more info.
Need in-depth examples?
Have a look at the tests!