Updating documents in Express - Mini Project: Build & Apply

Updating Documents with Express

📖 Scenario: You are building a simple web server that manages a list of books. Each book has a title and an author. You want to update the author of a specific book using Express.

🎯 Goal: Create an Express server with a route to update the author of a book by its title.

📋 What You'll Learn

Create an array called books with three book objects, each having title and author properties.

Create a variable called targetTitle with the value of the book title to update.

Use Array.prototype.find() to locate the book object with the title matching targetTitle and update its author property.

Add an Express PUT route at /books/:title that updates the author of the book with the given title.

💡 Why This Matters

🌍 Real World

Updating documents or records is a common task in web servers managing data like books, users, or products.

💼 Career

Understanding how to update data in Express routes is essential for backend development roles.

1

Create the initial books array

Create an array called books with these exact objects: { title: '1984', author: 'George Orwell' }, { title: 'Brave New World', author: 'Aldous Huxley' }, and { title: 'Fahrenheit 451', author: 'Ray Bradbury' }.

Express

// Create the books array with 3 book objects
// Your code here

Hint

Remember to create an array named books with three objects inside.

2

Set the target book title to update

Create a variable called targetTitle and set it to the string '1984'.

Express

const books = [
  { title: '1984', author: 'George Orwell' },
  { title: 'Brave New World', author: 'Aldous Huxley' },
  { title: 'Fahrenheit 451', author: 'Ray Bradbury' }
];

// Create targetTitle variable
// Your code here

Hint

Use const to create targetTitle and assign '1984'.

3

Find and update the book author

Use const bookToUpdate = books.find(book => book.title === targetTitle) to find the book. Then set bookToUpdate.author = 'Eric Arthur Blair' to update the author.

Express

const books = [
  { title: '1984', author: 'George Orwell' },
  { title: 'Brave New World', author: 'Aldous Huxley' },
  { title: 'Fahrenheit 451', author: 'Ray Bradbury' }
];

const targetTitle = '1984';

// Find the book and update its author
// Your code here

Hint

Use find() to get the book, then assign the new author.

4

Add Express PUT route to update author

Add an Express PUT route at /books/:title. Inside the route, find the book by req.params.title and update its author with req.body.author. Send back the updated book as JSON.

Express

const express = require('express');
const app = express();
app.use(express.json());

const books = [
  { title: '1984', author: 'George Orwell' },
  { title: 'Brave New World', author: 'Aldous Huxley' },
  { title: 'Fahrenheit 451', author: 'Ray Bradbury' }
];

const targetTitle = '1984';

const bookToUpdate = books.find(book => book.title === targetTitle);
bookToUpdate.author = 'Eric Arthur Blair';

// Add PUT route to update book author
// Your code here

Hint

Use app.put with req.params.title and req.body.author to update and respond.

Practice

1. What does the findByIdAndUpdate method do in Express with Mongoose?

easy

A. It updates a document by its ID and returns the updated document.

B. It deletes a document by its ID.

C. It creates a new document with a given ID.

D. It finds a document but does not update it.

Solution

1. Step 1: Understand the method purpose

   findByIdAndUpdate is used to find a document by its ID and update it with new data.

2. Step 2: Check the return value

   When used with { new: true }, it returns the updated document, not the old one.

3. Final Answer:

   It updates a document by its ID and returns the updated document. -> Option A

4. Quick Check:

   Update document by ID = A [OK]

Hint: Remember: findByIdAndUpdate updates and returns new data [OK]

Common Mistakes:

• Confusing update with delete operation
• Expecting it to create a new document
• Thinking it only finds without updating

2. Which of the following is the correct syntax to update a document by ID and return the updated document in Express with Mongoose?

easy

A. Model.findOneAndUpdate(id, update);

B. Model.updateById(id, update, callback);

C. Model.update(id, update, { returnNew: true });

D. Model.findByIdAndUpdate(id, update, { new: true }, callback);

Solution

1. Step 1: Identify correct method and parameters

   The correct method is findByIdAndUpdate with parameters: id, update object, options, and callback.

2. Step 2: Confirm option for returning updated document

   The option { new: true } ensures the updated document is returned.

3. Final Answer:

   Model.findByIdAndUpdate(id, update, { new: true }, callback); -> Option D

4. Quick Check:

   Correct syntax includes { new: true } = C [OK]

Hint: Use { new: true } option to get updated document [OK]

Common Mistakes:

• Using wrong method name like updateById
• Omitting the { new: true } option
• Passing incorrect parameters order

3. Given the code snippet:

Model.findByIdAndUpdate('123', { name: 'Alice' }, { new: true }, (err, doc) => {
  if (err) return console.error(err);
  console.log(doc.name);
});

What will be printed if the update is successful?

medium

A. The old name before update

B. Alice

C. undefined

D. An error message

Solution

1. Step 1: Understand the update and options

   The update changes the name to 'Alice' and { new: true } returns the updated document.

2. Step 2: Check the console output

   The callback logs doc.name, which will be 'Alice' after update.

3. Final Answer:

   Alice -> Option B

4. Quick Check:

   Updated document name logged = B [OK]

Hint: With { new: true }, console logs updated value [OK]

Common Mistakes:

• Expecting old value instead of updated
• Not using { new: true } option
• Misreading callback parameters

4. Identify the error in this code snippet for updating a document:

Model.findByIdAndUpdate('123', { age: 30 }, (err, doc) => {
  if (err) console.log(err);
  else console.log(doc);
});

medium

A. The update object should be a string

B. Using wrong method name, should be updateById

C. Missing the { new: true } option to get updated document

D. Callback function parameters are incorrect

Solution

1. Step 1: Check method usage

   The method findByIdAndUpdate is correct and callback parameters are valid.

2. Step 2: Identify missing option

   Without { new: true }, the returned document is the old one, not updated.

3. Final Answer:

   Missing the { new: true } option to get updated document -> Option C

4. Quick Check:

   Return updated doc requires { new: true } = D [OK]

Hint: Add { new: true } to get updated document in callback [OK]

Common Mistakes:

• Assuming updateById is a valid method
• Expecting updated doc without { new: true }
• Thinking update object must be string

5. You want to update a user's email only if the new email is not empty and valid. Which approach correctly updates the document safely in Express with Mongoose?

hard

A. Check email validity before calling findByIdAndUpdate, then update with { new: true } option.

B. Call findByIdAndUpdate directly without validation to save time.

C. Use findByIdAndUpdate with an empty update object if email is invalid.

D. Update the document without callback and ignore errors.

Solution

1. Step 1: Validate input before updating

   Always check if the new email is valid and not empty before updating to avoid bad data.

2. Step 2: Use findByIdAndUpdate with { new: true }

   Update the document with the valid email and use { new: true } to get the updated document.

3. Final Answer:

   Check email validity before calling findByIdAndUpdate, then update with { new: true } option. -> Option A

4. Quick Check:

   Validate input + update with new:true = A [OK]

Hint: Always validate input before updating documents [OK]

Common Mistakes:

• Skipping validation and risking bad data
• Updating with empty or invalid data
• Ignoring errors by not using callbacks