Structuring Express applications

In the examples provided in Creating a RESTFul API with Express, we had all our API routes being served via the app variable in index.js. This was very cluttered. It is best to structure your application by having a dedicated /routes/ directory and within this, a dedicated file for each route.

In general, the following application structure works well:

\
    routes\
    middlewear\
    config\
    public\

We will demonstrate this for the /courses route.

Using the `Router` object

Previously we instantiated an Expres instance with app:

const express = require('express')
const app = express()

When we partition our routes we can no longer do this, since we are only serving a single route, not the whole app, so we instead use Express's Router object:

const router = express.Router()

And then update all references to app with router, e.g:

router.get('/api/courses', (req, res) => {
 res.send(courses)
})

We would then export:

module.exports = router

Now all the functions pertaining to that route are handled in a dedicated file.

We would then import it within the main entry file, index.js and invoke it. The invocation syntax here is the same as when we utilise middlewear:

const courses = require('./routes/courses')
app.use('/api/courses', courses);

Given that we define the courses route in index.js as being served from /api/courses, we no longer have to use that slug within courses.js, we can change all our routes to / , e.g.

router.get('/', (req, res) => {
 res.send(courses)
})

app.get("/:id", (req, res) => {
  res.send(req.params.id);
});

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Structuring Express applications

Using the Router object

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Using the `Router` object