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Mongoose and Express CRUD Operations Highlights Reel

# Mongoose and Express CRUD Operations Highlights Reel

## 1. CREATE (Insert) Operation

```javascript // Define the schema const bookSchema = new mongoose.Schema({ title: String, author: { type: mongoose.Schema.Types.ObjectId, ref: 'Author' }, publishedYear: Number });

// Create the model const Book = mongoose.model('Book', bookSchema);

// Express route for creating a new book app.post('/api/books', async (req, res) => { const book = new Book({ title: req.body.title, author: req.body.authorId, publishedYear: req.body.publishedYear });

try { const newBook = await book.save(); res.status(201).json(newBook); } catch (err) { res.status(400).json({ message: err.message }); } }); ```

Key Points: - Mongoose schema defines the structure of the document - `new Book(...)` creates a new document instance - `book.save()` inserts the document into the MongoDB collection

## 2. READ Operations

### Read All ```javascript app.get('/api/books', async (req, res) => { try { const books = await Book.find().populate('author'); res.json(books); } catch (err) { res.status(500).json({ message: err.message }); } }); ```

### Read One ```javascript app.get('/api/books/:id', async (req, res) => { try { const book = await Book.findById(req.params.id).populate('author'); if (!book) return res.status(404).json({ message: 'Book not found' }); res.json(book); } catch (err) { res.status(500).json({ message: err.message }); } }); ```

Key Points: - `Book.find()` retrieves all documents - `Book.findById()` retrieves a single document by its ID - `.populate('author')` replaces the author ID with the full author document

## 3. UPDATE Operation

```javascript app.patch('/api/books/:id', async (req, res) => { try { const book = await Book.findById(req.params.id); if (!book) return res.status(404).json({ message: 'Book not found' }); if (req.body.title) book.title = req.body.title; if (req.body.authorId) book.author = req.body.authorId; if (req.body.publishedYear) book.publishedYear = req.body.publishedYear;

const updatedBook = await book.save(); res.json(updatedBook); } catch (err) { res.status(400).json({ message: err.message }); } }); ```

Key Points: - `Book.findById()` first retrieves the document - Update only the fields that are provided in the request - `book.save()` saves the updated document back to the database

## 4. DELETE Operation

```javascript app.delete('/api/books/:id', async (req, res) => { try { const book = await Book.findById(req.params.id); if (!book) return res.status(404).json({ message: 'Book not found' }); await book.remove(); res.json({ message: 'Book deleted' }); } catch (err) { res.status(500).json({ message: err.message }); } }); ```

Key Points: - `Book.findById()` first retrieves the document - `book.remove()` deletes the document from the database

## Summary

- Mongoose provides a schema-based solution to model your application data - Express routes handle HTTP requests and delegate database operations to Mongoose - Mongoose methods like `save()`, `find()`, `findById()`, and `remove()` map to CRUD operations - Async/await is used to handle asynchronous database operations - Error handling is crucial in each operation to provide proper feedback

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