REST vs GraphQL awareness in Express - Hands-On Comparison

REST vs GraphQL Awareness with Express

📖 Scenario: You are building a simple Express server to understand the difference between REST and GraphQL APIs. This will help you see how data can be requested and served in two different ways.

🎯 Goal: Create an Express server that has one REST endpoint and one GraphQL endpoint. The REST endpoint will return a list of books, and the GraphQL endpoint will allow querying the same books with flexible fields.

📋 What You'll Learn

Create an array called books with 3 book objects, each having id, title, and author properties

Create a variable called port set to 4000

Create a REST GET endpoint at /books that returns the books array as JSON

Set up a GraphQL schema with a Book type and a books query that returns the list of books

💡 Why This Matters

🌍 Real World

APIs are how apps talk to each other. REST and GraphQL are two popular ways to build APIs. Understanding both helps you choose the right tool for your project.

💼 Career

Many jobs require building or working with APIs. Knowing REST and GraphQL basics is essential for backend and full-stack developers.

1

DATA SETUP: Create the books array

Create an array called books with these exact 3 objects: { id: 1, title: '1984', author: 'George Orwell' }, { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' }, and { id: 3, title: 'Fahrenheit 451', author: 'Ray Bradbury' }.

Express

// Your code here

Hint

Use const books = [ ... ] with the exact objects inside.

2

CONFIGURATION: Set the server port

Create a variable called port and set it to 4000.

Express

const books = [
  { id: 1, title: '1984', author: 'George Orwell' },
  { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' },
  { id: 3, title: 'Fahrenheit 451', author: 'Ray Bradbury' }
];

// Your code here

Hint

Use const port = 4000; to set the port number.

3

CORE LOGIC: Create the REST GET endpoint

Create an Express app with const app = express(). Then add a GET endpoint at /books that sends the books array as JSON using res.json(books).

Express

const books = [
  { id: 1, title: '1984', author: 'George Orwell' },
  { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' },
  { id: 3, title: 'Fahrenheit 451', author: 'Ray Bradbury' }
];

const port = 4000;

// Your code here

Hint

Use const app = express() and app.get('/books', (req, res) => res.json(books)).

4

COMPLETION: Add GraphQL schema and endpoint

Import graphqlHTTP from express-graphql and buildSchema from graphql. Create a GraphQL schema with a Book type having id, title, and author fields. Add a books query returning the list of books. Then add a GraphQL endpoint at /graphql using app.use with graphqlHTTP, passing the schema and a root resolver that returns books. Finally, start the server listening on port with app.listen(port).

Express

const express = require('express');
const books = [
  { id: 1, title: '1984', author: 'George Orwell' },
  { id: 2, title: 'The Hobbit', author: 'J.R.R. Tolkien' },
  { id: 3, title: 'Fahrenheit 451', author: 'Ray Bradbury' }
];

const port = 4000;

const app = express();

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

// Your code here

Hint

Use buildSchema to define the schema and graphqlHTTP middleware for the /graphql route.

Practice

1. Which statement best describes the main difference between REST and GraphQL in an Express API?

easy

A. REST uses multiple URLs and HTTP methods; GraphQL uses a single URL with flexible queries.

B. REST uses a single URL and flexible queries; GraphQL uses multiple URLs and HTTP methods.

C. REST and GraphQL both use multiple URLs but differ in data format.

D. REST and GraphQL are identical in how they handle data fetching.

Solution

1. Step 1: Understand REST API structure

   REST APIs use different URLs (endpoints) for different resources and HTTP methods like GET, POST, PUT, DELETE to perform actions.

2. Step 2: Understand GraphQL API structure

   GraphQL uses a single endpoint URL and clients specify exactly what data they want in the query, making it flexible.

3. Final Answer:

   REST uses multiple URLs and HTTP methods; GraphQL uses a single URL with flexible queries. -> Option A

4. Quick Check:

   REST vs GraphQL = multiple URLs vs single URL [OK]

Hint: REST = many URLs; GraphQL = one URL with queries [OK]

Common Mistakes:

• Thinking GraphQL uses multiple URLs like REST
• Confusing HTTP methods usage between REST and GraphQL
• Believing REST and GraphQL are the same

2. Which Express route setup correctly represents a REST API endpoint for getting a user by ID?

easy

A. app.put('/user', (req, res) => { /* fetch user */ });

B. app.post('/user/:id', (req, res) => { /* fetch user */ });

C. app.get('/user/:id', (req, res) => { /* fetch user */ });

D. app.get('/graphql', (req, res) => { /* fetch user */ });

Solution

1. Step 1: Identify correct HTTP method for fetching data

   GET method is used to retrieve data in REST APIs.

2. Step 2: Check URL pattern for resource identification

   /user/:id correctly uses a URL parameter to specify which user to fetch.

3. Final Answer:

   app.get('/user/:id', (req, res) => { /* fetch user */ }); -> Option C

4. Quick Check:

   GET + /user/:id = fetch user [OK]

Hint: GET method + URL with :id fetches resource [OK]

Common Mistakes:

• Using POST instead of GET for fetching data
• Using GraphQL endpoint for REST question
• Using PUT method which is for updates

3. Given this Express GraphQL setup, what will the client receive when querying for { user(id: "1") { name } }?

const { graphqlHTTP } = require('express-graphql');
const schema = buildSchema(`
  type Query {
    user(id: ID!): User
  }
  type User {
    id: ID
    name: String
    email: String
  }
`);
const root = {
  user: ({ id }) => ({ id, name: 'Alice', email: '[e-mail]' })
};
app.use('/graphql', graphqlHTTP({ schema, rootValue: root, graphiql: true }));

medium

A. {"data":{"user":{"id":"1","name":"Alice","email":"[e-mail]"}}}

B. {"data":{"user":{"name":"Alice"}}}

C. {"error":"Field 'user' not found"}

D. {"data":{"user":null}}

Solution

1. Step 1: Understand the GraphQL query

   The query requests only the name field of the user with id "1".

2. Step 2: Check resolver returns full user object

   The resolver returns id, name, and email, but GraphQL returns only requested fields.

3. Final Answer:

   {"data":{"user":{"name":"Alice"}}} -> Option B

4. Quick Check:

   GraphQL returns only requested fields [OK]

Hint: GraphQL returns only requested fields, not full object [OK]

Common Mistakes:

• Expecting all fields returned regardless of query
• Confusing error responses with valid data
• Assuming REST style full object return

4. Identify the error in this Express REST route that causes it to always return an empty response:

app.get('/users/:id', (req, res) => {
  const user = users.find(u => u.id === req.params.id);
  if (user) {
    res.json(user);
  }
  res.end();
});

medium

A. The route path should be '/user/:id' not '/users/:id'.

B. The route should use POST instead of GET.

C. The user lookup uses incorrect comparison operator.

D. res.end() is called even after sending a response, causing empty output.

Solution

1. Step 1: Analyze response flow

   If user is found, res.json(user) sends response, but code continues to res.end() which sends empty response again.

2. Step 2: Understand Express response behavior

   Calling res.end() after res.json() can cause the response to be overwritten or cause errors.

3. Final Answer:

   res.end() is called even after sending a response, causing empty output. -> Option D

4. Quick Check:

   Only send one response per request [OK]

Hint: Send only one response; avoid res.end() after res.json() [OK]

Common Mistakes:

• Using wrong HTTP method for fetching
• Assuming path name causes empty response
• Ignoring that res.end() can overwrite response

5. You want to build an Express API that allows clients to fetch user data with flexible fields and avoid multiple endpoints. Which approach is best and why?

hard

A. Use GraphQL with a single endpoint letting clients specify exactly which fields they want.

B. Use REST but return all fields for every resource to avoid multiple endpoints.

C. Use REST with multiple endpoints for each resource and HTTP methods for actions.

D. Use GraphQL but create multiple endpoints for each query type.

Solution

1. Step 1: Identify requirement for flexible fields and fewer endpoints

   Clients want to specify fields and avoid many URLs.

2. Step 2: Match approach to requirement

   GraphQL uses one endpoint and allows clients to request exactly needed fields, fitting the requirement.

3. Final Answer:

   Use GraphQL with a single endpoint letting clients specify exactly which fields they want. -> Option A

4. Quick Check:

   Flexible fields + single endpoint = GraphQL [OK]

Hint: Flexible data + one URL = GraphQL [OK]

Common Mistakes:

• Choosing REST and returning all fields wastes bandwidth
• Using GraphQL with multiple endpoints defeats its purpose
• Confusing REST flexibility with GraphQL's query power