Demo Copilot Chat

Explore how GitHub Copilot Chat can scaffold, debug, and document a Node.js REST API using slash commands and contextual understanding.

Scaffolding a Node.js REST API

Start by asking Copilot Chat to generate a minimal Express server with an in-memory users database (id, firstName, lastName, email). It instantly produces server.js:

// server.js
const express = require('express');
const bodyParser = require('body-parser');

const app = express();
const port = 3000;

app.use(bodyParser.json());

let database = [];
let idCounter = 1;

// Retrieve all users
app.get('/users', (req, res) => {
  res.json(database);
});

// Retrieve a user by ID
app.get('/users/:id', (req, res) => {
  const user = database.find(u => u.id === parseInt(req.params.id));
  if (user) {
    res.json(user);
  } else {
    res.status(404).send('User not found');
  }
});

// Create a new user
app.post('/users', (req, res) => {
  const { firstName, lastName, email } = req.body;
  const newUser = { id: idCounter++, firstName, lastName, email };
  database.push(newUser);
  res.status(201).json(newUser);
});

// Update an existing user
app.put('/users/:id', (req, res) => {
  const { firstName, lastName, email } = req.body;
  const user = database.find(u => u.id === parseInt(req.params.id));
  if (user) {
    user.firstName = firstName;
    user.lastName = lastName;
    user.email = email;
    res.json(user);
  } else {
    res.status(404).send('User not found');
  }
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

Using /new to Scaffold Files

Instead of manually writing the code, use the /new slash command to bootstrap an entire project:

/new create a Node application API

Copilot Chat generates an index.js with a standard Express setup:

// index.js
const express = require('express');

const app = express();
const port = 3000;

app.use(express.json());

let users = [];

// Create a new user
app.post('/users', (req, res) => {
  const { id, firstName, lastName, email } = req.body;
  const newUser = { id, firstName, lastName, email };
  users.push(newUser);
  res.status(201).json(newUser);
});

// Get all users
app.get('/users', (req, res) => {
  res.json(users);
});

// Get a single user
app.get('/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  if (user) {
    res.json(user);
  } else {
    res.status(404).send('User not found');
  }
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

Adding package.json and Splitting into app.js

To turn this into a maintainable Node.js application, Copilot Chat introduces a package.json and refactors the server:

// package.json
{
  "name": "weatherdemo",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "test": "jest"
  },
  "dependencies": {
    "express": "^4.17.1"
  },
  "devDependencies": {
    "jest": "^27.0.6",
    "supertest": "^6.1.3"
  }
}

Now index.js simply starts the server:

// index.js
const app = require('./app');
const port = 3000;

app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});

And app.js holds all request handlers:

// app.js
const express = require('express');
const app = express();

app.use(express.json());

let users = [];

// Create user
app.post('/users', (req, res) => {
  const { id, firstName, lastName, email } = req.body;
  const newUser = { id, firstName, lastName, email };
  users.push(newUser);
  res.status(201).json(newUser);
});

// List users
app.get('/users', (req, res) => {
  res.json(users);
});

// Get user
app.get('/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  if (user) {
    res.json(user);
  } else {
    res.status(404).send('User not found');
  }
});

// Delete user
app.delete('/users/:id', (req, res) => {
  const index = users.findIndex(u => u.id === parseInt(req.params.id));
  if (index !== -1) {
    users.splice(index, 1);
    res.status(204).send();
  } else {
    res.status(404).send('User not found');
  }
});

module.exports = app;

Generating Tests

Copilot Chat can scaffold a comprehensive test suite with Jest and Supertest:

// __tests__/app.test.js
const request = require('supertest');
const app = require('../app');

describe('User API', () => {
  it('should create a new user', async () => {
    const res = await request(app)
      .post('/users')
      .send({ id: 1, firstName: 'John', lastName: 'Doe', email: '[email protected]' });
    expect(res.statusCode).toBe(201);
    expect(res.body).toHaveProperty('id', 1);
  });

  it('should retrieve all users', async () => {
    const res = await request(app).get('/users');
    expect(res.statusCode).toBe(200);
    expect(res.body.length).toBeGreaterThan(0);
  });

  it('should retrieve a user by ID', async () => {
    const res = await request(app).get('/users/1');
    expect(res.statusCode).toBe(200);
    expect(res.body).toHaveProperty('id', 1);
  });

  it('should delete a user and return 404 on next fetch', async () => {
    await request(app).delete('/users/1');
    const res = await request(app).get('/users/1');
    expect(res.statusCode).toBe(404);
  });
});

Installing and Running

1. Install dependencies:

   npm install
   

2. Start the server:

   npm start
   

   You’ll see:

   > [email protected] start
   > node index.js
   
   Server is running on http://localhost:3000
   

3. Test your API endpoints:
   • GET http://localhost:3000/users → []
   • POST http://localhost:3000/users (JSON payload) → creates a user

Working Set & Context

Copilot Chat leverages your working set—open files, recent edits, tests, and terminal output—to deliver contextual suggestions and reduce manual highlighting.

Key Slash Commands

Generating Documentation

Easily ask Copilot Chat to generate API docs without manual comments:

/**
 * @api {get} /users Retrieve all users
 * @apiName GetUsers
 * @apiGroup User
 *
 * @apiSuccess {Object[]} users List of user objects.
 * @apiSuccess {Number} id User’s unique ID.
 * @apiSuccess {String} firstName First name.
 * @apiSuccess {String} lastName Last name.
 * @apiSuccess {String} email Email address.
 *
 * @apiSuccessExample {json} Success-Response:
 *     HTTP/1.1 200 OK
 *     [
 *       { "id": 1, "firstName": "John", "lastName": "Doe", "email": "[email protected]" }
 *     ]
 */
app.get('/users', (req, res) => { … });

Switching AI Models

You can toggle between backends (e.g., ChatGPT-4, Claude) via the model dropdown in Copilot Chat to find the best fit for your workflow.

Links and References

• GitHub Copilot Chat
• Express.js Documentation
• Node.js Official Site
• Jest
• Supertest