Creating documents in Express - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new document in Express using Mongoose.

Express

const newUser = new User({ name: 'Alice', age: 25 });
newUser.[1]();

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

Adelete

Bsave

Cupdate

Dfind

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'find' instead of 'save' to create a document.

Trying to update or delete before saving the document.

The save() method saves the new document to the database.

2fill in blank

medium

Complete the code to create and save a new product document asynchronously.

Express

async function addProduct() {
  const product = new Product({ name: 'Book', price: 15 });
  await product.[1]();
}

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

AupdateOne

Bremove

CfindOne

Dsave

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remove' which deletes documents.

Using 'findOne' which searches documents instead of saving.

Using await product.save() saves the new product document asynchronously.

3fill in blank

hard

Fix the error in the code to correctly create a new user document.

Express

const user = new User({ username: 'john' });
user.[1]();

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

Asave

Bcreate

Cfind

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'create' on an instance instead of the model.

Not using 'new' keyword to create the document.

You must use new User() to create a document instance before calling save().

4fill in blank

hard

Fill both blanks to create and save a new blog post document with a title and content.

Express

const post = new Post({ title: [1], content: [2] });
await post.save();

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

A'My Day'

B'Hello World'

C'This is my first post.'

D'Sample content'

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted strings causing syntax errors.

Mixing up title and content values.

The title should be a string like 'Hello World' and content a string like 'This is my first post.' to create a meaningful blog post.

5fill in blank

hard

Fill all three blanks to create a new comment document and save it asynchronously.

Express

async function addComment() {
  const comment = new Comment({
    author: [1],
    text: [2],
    date: [3]
  });
  await comment.save();
}

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

A'Alice'

B'Great post!'

Cnew Date()

D'2023-01-01'

Attempts:

3 left

💡 Hint

Common Mistakes

Using date as a string instead of a Date object.

Forgetting quotes around author or text.

The author and text are strings, so they need quotes. The date is a Date object created with new Date().

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