Last Sync: 2022-04-30 15:00:04

Programming_Languages/NodeJS/Structuring_Express_applications.md

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+---
+tags:
+  - Programming_Languages
+  - backend
+  - node-js
+  - express
+  - rest
+---
+
+# Structuring Express applications
+
+In the examples provided in [Creating a RESTFul API with Express](./Create_RESTful_API_with_Express.md), 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`:
+
+```js
+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:
+
+```js
+const router = express.Router()
+```
+
+And then update all references to `app` with `router`, e.g:
+```js
+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](./Middleware.md): 
+
+```js
+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. 
+
+```js
+router.get('/', (req, res) => {
+ res.send(courses)
+})
+```
+````js
+app.get("/:id", (req, res) => {
+  res.send(req.params.id);
+});