Maintaining

Although pull requests and issues are welcome, the Aufentic team will keep this package and repository up to date.

Original repository thanks to bmullan91.

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 @aufentic/express-subdomain --save

Support for ES modules

import subdomain from 'express-subdomain';
import express from '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"}]"

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.internal
127.0.0.1       subdomain.myapp.internal

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 https://github.com/bmullan91/express-subdomain/issues/17 for more info.