POST route handling in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a POST route for '/submit'.

Express

app.[1]('/submit', (req, res) => {
  res.send('Form submitted');
});

Drag options to blanks, or click blank then click option'

Aget

Bpost

Cput

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'get' instead of 'post' for form submission routes.

Using 'put' or 'delete' which are for other HTTP actions.

The post method defines a POST route in Express.

2fill in blank

medium

Complete the code to access JSON data sent in the POST request body.

Express

app.post('/data', (req, res) => {
  const userData = req.[1];
  res.json(userData);
});

Drag options to blanks, or click blank then click option'

Aparams

Bheaders

Cquery

Dbody

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'params' which is for URL parameters.

Using 'query' which is for URL query strings.

The body property contains data sent in the POST request body.

3fill in blank

hard

Fix the error in the code to parse JSON body data correctly.

Express

const express = require('express');
const app = express();

app.[1](express.json());

app.post('/info', (req, res) => {
  res.send(req.body);
});

Drag options to blanks, or click blank then click option'

Ause

Bpost

Clisten

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'post' instead of 'use' for middleware.

Not adding JSON parsing middleware at all.

The use method adds middleware to parse JSON bodies before routes handle requests.

4fill in blank

hard

Fill both blanks to send a JSON response with a status code 201.

Express

app.post('/create', (req, res) => {
  res.[1](201).[2]({ message: 'Created' });
});

Drag options to blanks, or click blank then click option'

Astatus

Bjson

Csend

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' instead of 'json' for JSON responses.

Not setting the status code properly.

Use status(201) to set the HTTP status code and json() to send a JSON response.

5fill in blank

hard

Fill all three blanks to create a POST route that reads JSON body, logs it, and responds with a success message.

Express

app.[1]('/log', (req, res) => {
  const data = req.[2];
  console.log(data);
  res.[3]({ status: 'success' });
});

Drag options to blanks, or click blank then click option'

Apost

Bbody

Cjson

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'get' instead of 'post' for the route.

Trying to access data from 'params' or 'query' instead of 'body'.

Using 'send' instead of 'json' for the response.

Define a POST route with post, access the JSON body with body, and respond with JSON using json.

Practice

1. What does the app.post method in Express do?

easy

A. It defines a route that handles HTTP GET requests.

B. It defines a route that handles HTTP POST requests.

C. It starts the Express server.

D. It sends a response to the client automatically.

Solution

1. Step 1: Understand HTTP methods in Express

   Express uses different methods like app.get and app.post to handle different HTTP request types.

2. Step 2: Identify the purpose of app.post

   app.post specifically handles POST requests, which are used to send data to the server.

3. Final Answer:

   It defines a route that handles HTTP POST requests. -> Option B

4. Quick Check:

   POST route = app.post [OK]

Hint: POST routes handle data sent by clients via app.post [OK]

Common Mistakes:

• Confusing POST with GET routes
• Thinking app.post starts the server
• Assuming app.post sends responses automatically

2. Which of the following is the correct syntax to create a POST route in Express for path /submit?

easy

A. app.post('/submit', (req, res) => res.send('Received'));

B. app.get('/submit', (req, res) => { res.send('Received'); });

C. app.post('/submit', (res, req) => { res.send('Received'); });

D. app.post('/submit', (req, res) => { res.send('Received'); });

Solution

1. Step 1: Check method and path

   The method should be app.post and path '/submit'.

2. Step 2: Verify callback parameters and syntax

   The callback function must have parameters (req, res) in that order, and the response should be sent inside the function body.

3. Final Answer:

   app.post('/submit', (req, res) => { res.send('Received'); }); -> Option D

4. Quick Check:

   Correct syntax = app.post('/submit', (req, res) => { res.send('Received'); }); [OK]

Hint: Use app.post(path, (req, res) => { }) with req first [OK]

Common Mistakes:

• Swapping req and res parameters
• Using app.get instead of app.post
• Omitting curly braces in arrow function

3. Given this Express code snippet, what will be the response when a POST request with JSON body {"name":"Alice"} is sent to /hello?

const express = require('express');
const app = express();
app.use(express.json());
app.post('/hello', (req, res) => {
  res.send(`Hello, ${req.body.name}!`);
});

medium

A. "Hello, Alice!"

B. "Hello, undefined!"

C. SyntaxError

D. 404 Not Found

Solution

1. Step 1: Check middleware for JSON parsing

   The code uses app.use(express.json()) which parses JSON bodies into req.body.

2. Step 2: Understand route handler response

   The handler sends a string using the name property from req.body. Since the body has {"name":"Alice"}, it will respond with "Hello, Alice!".

3. Final Answer:

   "Hello, Alice!" -> Option A

4. Quick Check:

   JSON body parsed correctly = "Hello, Alice!" [OK]

Hint: Use express.json() to access req.body data [OK]

Common Mistakes:

• Forgetting to add express.json() middleware
• Expecting req.body to be undefined
• Confusing POST with GET routes

4. What is wrong with this Express POST route code?

app.post('/data', (req, res) => {
  console.log(req.body);
  res.send('Data received');
});

Assuming the client sends JSON data in the request body.

medium

A. Route path should be '/post' instead of '/data'.

B. Callback function parameters are reversed.

C. Missing middleware to parse JSON body.

D. res.send should be called before console.log.

Solution

1. Step 1: Check for JSON parsing middleware

   The code does not show app.use(express.json()), which is needed to parse JSON request bodies into req.body.

2. Step 2: Understand effect of missing middleware

   Without JSON parsing middleware, req.body will be undefined, so logging it won't show the sent data.

3. Final Answer:

   Missing middleware to parse JSON body. -> Option C

4. Quick Check:

   express.json() middleware required = Missing middleware to parse JSON body. [OK]

Hint: Always add express.json() to parse JSON POST bodies [OK]

Common Mistakes:

• Assuming req.body works without middleware
• Swapping req and res parameters
• Thinking route path name matters for parsing

5. You want to create a POST route /register that accepts JSON data with username and password. It should respond with { success: true, user: username }. Which code correctly implements this?

hard

A. app.post('/register', express.json(), (req, res) => {
const { username, password } = req.body;
res.json({ success: true, user: username });
});

B. app.post('/register', (req, res) => {
const { username, password } = req.body;
res.json({ success: true, user: username });
});

C. app.post('/register', (req, res) => {
const { username, password } = req.query;
res.json({ success: true, user: username });
});

D. app.post('/register', (req, res) => {
const { username, password } = req.body;
res.send({ success: true, user: username });
});

Solution

1. Step 1: Ensure JSON body parsing middleware is used

   app.post('/register', express.json(), (req, res) => { const { username, password } = req.body; res.json({ success: true, user: username }); }); uses express.json() as middleware for this route, so req.body will be parsed correctly.

2. Step 2: Check response format and data source

   It extracts username and password from req.body and responds with JSON using res.json(), which is correct.

3. Final Answer:

   Option A correctly implements the POST route with JSON parsing and response. -> Option A

4. Quick Check:

   Use express.json() middleware and res.json() for JSON response [OK]

Hint: Add express.json() middleware and use res.json() to respond [OK]

Common Mistakes:

• Not using JSON parsing middleware
• Reading data from req.query instead of req.body
• Using res.send instead of res.json for JSON response