REST vs GraphQL awareness in Express - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding REST API request methods

Which HTTP method is typically used in REST APIs to update an entire resource?

A PUT

B POST

C GET

D DELETE

💡 Hint

Think about which method replaces the whole resource.

In REST, PUT is used to update or replace an entire resource. POST is usually for creating, GET for reading, and DELETE for removing.

❓ component_behavior

intermediate

GraphQL query response shape

Given a GraphQL query requesting only the name and age fields of a user, what will the response JSON look like?

Express

query { user(id: "1") { name age } }

A {"data": {"user": {"name": "Alice"}}}

B {"user": {"name": "Alice", "age": 30}}

C {"data": {"user": {"id": "1", "name": "Alice", "age": 30}}}

D {"data": {"user": {"name": "Alice", "age": 30}}}

💡 Hint

GraphQL responses always wrap data inside a 'data' key.

GraphQL responses wrap the requested data inside a data object. Only the requested fields appear. Here, name and age are included, but not id.

📝 Syntax

advanced

Express route for REST vs GraphQL

Which Express route setup correctly handles a GraphQL POST request at '/graphql'?

Express

const express = require('express');
const app = express();
// Which option is correct?

A app.post('/graphql', (req, res) => { res.send('GraphQL endpoint'); });

B app.get('/graphql', (req, res) => { res.send('GraphQL endpoint'); });

C app.delete('/graphql', (req, res) => { res.send('GraphQL endpoint'); });

D app.put('/graphql', (req, res) => { res.send('GraphQL endpoint'); });

💡 Hint

GraphQL queries and mutations are usually sent via POST requests.

GraphQL servers typically accept POST requests at a single endpoint, often '/graphql'. Using app.post matches this pattern.

❓ state_output

advanced

REST API response status codes

What HTTP status code should a REST API return after successfully deleting a resource?

A 200 OK

B 201 Created

C 204 No Content

D 404 Not Found

💡 Hint

The response usually has no body after deletion.

After a successful deletion, REST APIs commonly return 204 No Content to indicate success without a response body.

🔧 Debug

expert

Debugging GraphQL query error in Express

An Express server with GraphQL returns an error: Cannot read property 'data' of undefined. Which code snippet is the likely cause?

Express

app.post('/graphql', async (req, res) => {
  const result = await graphql(schema, req.body.query);
  res.json(result.data);
});

A The 'graphql' function returns a promise resolving to an object with 'data' property, so this code is correct.

B The 'graphql' function returns a promise resolving to an object with 'data' and 'errors', but the code should check if 'result' is defined before accessing 'result.data'.

C The 'graphql' function returns a promise resolving to an object with 'data' and 'errors', but if 'result' is undefined, accessing 'result.data' causes the error.

D The 'graphql' function returns an object with 'data' nested inside 'result', so accessing 'result.data' is correct.

💡 Hint

Check if the promise resolves correctly and if the result is defined before accessing properties.

The error occurs because result might be undefined if the promise rejects or the call fails. The code should handle errors and check if result exists before accessing result.data.