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2020-05-16 21:54:42 +08:00

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# Separate Express 'app' and 'server'
<br/><br/>
### One Paragraph Explainer
The latest Express generator comes with a great practice that is worth to keep - the API declaration is separated from the network related configuration (port, protocol, etc). This allows testing the API in-process, without performing network calls, with all the benefits that it brings to the table: fast testing execution and getting coverage metrics of the code. It also allows deploying the same API under flexible and different network conditions. Bonus: better separation of concerns and cleaner code
<br/><br/>
### Code example: API declaration, should reside in app.js/app.ts
```javascript
const app = express();
app.use(bodyParser.json());
app.use('/api/events', events.API);
app.use('/api/forms', forms);
```
### Code example: Server network declaration, should reside in /bin/www
<details>
<summary><strong>Javascript</strong></summary>
```javascript
const app = require('../app');
const http = require('http');
// Get port from environment and store in Express.
const port = normalizePort(process.env.PORT || '3000');
app.set('port', port);
// Create HTTP server.
const server = http.createServer(app);
```
</details>
<details>
<summary><strong>Typescript</strong></summary>
```typescript
import app from '../app';
import http from 'http';
// Get port from environment and store in Express.
const port = normalizePort(process.env.PORT || '3000');
app.set('port', port);
// Create HTTP server.
const server = http.createServer(app);
```
</details>
### Example: test your API in-process using supertest (popular testing package)
<details>
<summary><strong>Javascript</strong></summary>
```javascript
const request = require('supertest');
const app = express();
app.get('/user', (req, res) => {
res.status(200).json({ name: 'tobi' });
});
request(app)
.get('/user')
.expect('Content-Type', /json/)
.expect('Content-Length', '15')
.expect(200)
.end((err, res) => {
if (err) throw err;
});
```
</details>
<details>
<summary><strong>Typescript</strong></summary>
```typescript
import * as request from "supertest";
const app = express();
app.get('/user', (req: Request, res: Response) => {
res.status(200).json({ name: 'tobi' });
});
request(app)
.get('/user')
.expect('Content-Type', /json/)
.expect('Content-Length', '15')
.expect(200)
.end((err: Error) => {
if (err) throw err;
});
```
</details>