Creating documents in Express - Try It Yourself

Creating Documents with Express

📖 Scenario: You are building a simple web server that can create and serve text documents on request. This is useful for generating reports, notes, or any text content dynamically.

🎯 Goal: Build an Express server that creates a text document from given data and serves it to the user when they visit a specific URL.

📋 What You'll Learn

Create an Express app instance

Set up a route to handle GET requests at /document

Generate a text document content dynamically

Send the generated document as a downloadable file to the client

💡 Why This Matters

🌍 Real World

Web servers often need to generate and send files like reports, invoices, or logs dynamically to users.

💼 Career

Knowing how to create and serve files with Express is a common task for backend developers working with Node.js.

1

Set up Express app

Create a variable called express by requiring the 'express' module. Then create an Express app instance called app by calling express().

Express

const express = require('express');
const app = express();
// Your code here

Hint

Use require('express') to import Express and then call it as a function to create the app.

2

Create document content variable

Create a variable called documentContent and assign it the string 'This is a sample document created with Express.'.

Express

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

// Create documentContent variable
// Your code here

Hint

Assign the exact string to documentContent.

3

Add route to serve document

Use app.get to create a route for '/document'. Inside the route handler, use res.setHeader to set 'Content-Disposition' to 'attachment; filename="sample.txt"' and 'Content-Type' to 'text/plain'. Then send documentContent as the response using res.send(documentContent).

Express

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

const documentContent = 'This is a sample document created with Express.';

// Add GET route for '/document'
// Your code here

Hint

Use app.get with '/document' and set headers before sending the content.

4

Start the Express server

Use app.listen to start the server on port 3000. Provide a callback function that logs 'Server running on port 3000' to the console.

Express

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

const documentContent = 'This is a sample document created with Express.';

app.get('/document', (req, res) => {
    res.setHeader('Content-Disposition', 'attachment; filename="sample.txt"');
    res.setHeader('Content-Type', 'text/plain');
    res.send(documentContent);
});

// Start server on port 3000
// Your code here

Hint

Use app.listen(3000, () => { console.log(...) }) to start the server.

Practice

1. Which Express method is used to handle creating new documents via HTTP POST requests?

easy

A. app.post()

B. app.get()

C. app.put()

D. app.delete()

Solution

1. Step 1: Understand HTTP methods in Express

   Express uses different methods like get, post, put, and delete to handle HTTP requests.

2. Step 2: Identify method for creating new data

   The post method is used to create new documents or data entries.

3. Final Answer:

   app.post() -> Option A

4. Quick Check:

   Creating documents = app.post() [OK]

Hint: Use app.post() for creating new data entries [OK]

Common Mistakes:

• Using app.get() instead of app.post()
• Confusing app.put() with app.post()
• Using app.delete() for creation

2. Which code snippet correctly enables JSON parsing middleware in Express to access req.body?

easy

A. app.use(express.urlencoded());

B. app.use(express.json());

C. app.use(bodyParser.text());

D. app.use(express.static('public'));

Solution

1. Step 1: Identify middleware for JSON parsing

   Express provides express.json() middleware to parse JSON request bodies.

2. Step 2: Match correct usage

   The correct way is app.use(express.json()); to enable JSON parsing.

3. Final Answer:

   app.use(express.json()); -> Option B

4. Quick Check:

   JSON parsing middleware = express.json() [OK]

Hint: Use app.use(express.json()) to read JSON body [OK]

Common Mistakes:

• Using express.urlencoded() for JSON data
• Using bodyParser.text() instead of JSON parser
• Forgetting to enable any parser middleware

3. What will be the HTTP status code sent when the following Express route successfully creates a document?

app.post('/items', (req, res) => {
  // Assume document creation here
  res.status(201).send('Created');
});

medium

A. 200

B. 500

C. 400

D. 201

Solution

1. Step 1: Understand HTTP status codes for creation

   Status code 201 means "Created" and is used when a new resource is successfully created.

2. Step 2: Check the code's status method

   The code uses res.status(201), so it sends status 201.

3. Final Answer:

   201 -> Option D

4. Quick Check:

   Creation success status = 201 [OK]

Hint: Use status 201 for successful creation responses [OK]

Common Mistakes:

• Assuming 200 means creation success
• Using 400 or 500 for successful creation
• Not setting status code explicitly

4. Identify the error in this Express route for creating a document:

app.post('/users', (req, res) => {
  const user = req.body;
  saveUser(user);
  res.send('User created');
});

medium

A. saveUser function is not asynchronous

B. Using res.send instead of res.json

C. Missing JSON parsing middleware to read req.body

D. Route should use app.get instead of app.post

Solution

1. Step 1: Check access to req.body

   Without JSON parsing middleware, req.body will be undefined.

2. Step 2: Identify missing middleware

   The code does not show app.use(express.json()), so req.body won't work.

3. Final Answer:

   Missing JSON parsing middleware to read req.body -> Option C

4. Quick Check:

   Missing express.json() causes req.body undefined [OK]

Hint: Always enable express.json() before accessing req.body [OK]

Common Mistakes:

• Thinking res.send must be res.json
• Using app.get for creation routes
• Assuming saveUser must be async here

5. You want to create an Express route that accepts JSON data to create a new product and respond with the created product including an ID. Which code snippet correctly implements this?

hard

A. app.post('/products', (req, res) => {
const product = req.body;
product.id = Date.now();
res.status(201).json(product);
});

B. app.get('/products', (req, res) => {
const product = req.body;
product.id = Date.now();
res.json(product);
});

C. app.post('/products', (req, res) => {
const product = req.query;
product.id = Date.now();
res.status(200).send(product);
});

D. app.post('/products', (req, res) => {
const product = req.body;
res.send('Product created');
});

Solution

1. Step 1: Use correct HTTP method and access JSON body

   The route uses app.post and accesses req.body which is correct for creating a product.

2. Step 2: Add an ID and respond with status 201 and JSON

   Assigning product.id = Date.now() simulates creating an ID. Responding with res.status(201).json(product) sends the created product with proper status.

3. Final Answer:

   Option A code snippet -> Option A

4. Quick Check:

   POST + req.body + status 201 + json response = app.post('/products', (req, res) => { const product = req.body; product.id = Date.now(); res.status(201).json(product); }); [OK]

Hint: Use app.post with req.body and res.status(201).json() [OK]

Common Mistakes:

• Using app.get instead of app.post
• Reading data from req.query instead of req.body
• Not sending status 201 on creation