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}`);
});

You can tailor the /new command with additional options (e.g., include TypeScript or middleware) to fit your project needs.

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: 'john.doe@example.com' });
    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

Install dependencies:
npm install

Start the server:

npm start

You’ll see:

> weatherdemo@1.0.0 start
> node index.js

Server is running on http://localhost:3000

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

Command	Description	Example
`/new`	Scaffold new files or entire projects	`/new create a Node.js REST API`
`/fix`	Apply fixes to selected code or entire file	Highlight code, run `/fix`
`/terminal last command`	Explain your last shell command and its output	`/terminal last command`
`/terminal selection`	Analyze a selected block of terminal output	Highlight output, run `/terminal selection`
`#` (hashtag)	Attach context tags like `#changes`, `#codebase`, `#file selection`	Use `#changes` in your prompt
`/help`	Show usage tips based on the current editor file	`/help`
`/clear`	Clear the current conversation	`/clear`

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": "john.doe@example.com" }
 *     ]
 */
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.

Introduction

GitHub Copilot Basics

Prompt Engineering with Copilot

Advanced Features

Management of GitHub Copilot

Using Copilot Efficiently

Scaffolding a Node.js REST API

Using `/new` to Scaffold Files

Adding package.json and Splitting into app.js

Generating Tests

Installing and Running

Working Set & Context

Key Slash Commands

Generating Documentation

Switching AI Models

Links and References

Watch Video

​Scaffolding a Node.js REST API

​Using /new to Scaffold Files

​Adding package.json and Splitting into app.js

​Generating Tests

​Installing and Running

​Working Set & Context

​Key Slash Commands

​Generating Documentation

​Switching AI Models

​Links and References

Watch Video

Scaffolding a Node.js REST API

Using `/new` to Scaffold Files

Adding package.json and Splitting into app.js

Generating Tests

Installing and Running

Working Set & Context

Key Slash Commands

Generating Documentation

Switching AI Models

Links and References