CRUD Operations in REST APIs

🌍 Introduction

CRUD stands for Create, Read, Update, and Delete—the four fundamental operations used to manage resources in a RESTful API.

Each CRUD operation is mapped to an HTTP method:

Operation	HTTP Method	Description
Create	POST	Add a new resource
Read	GET	Retrieve an existing resource
Update	PUT or PATCH	Modify an existing resource
Delete	DELETE	Remove a resource

In this lesson, you’ll learn:

• How CRUD maps to RESTful APIs.
• When to use POST, GET, PUT, PATCH, DELETE.
• The structure of CRUD endpoints.

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📌 1. Understanding CRUD Operations

✅ 1️⃣ Create (POST)

Used to add new data to the server.

Example: Creating a new user

POST /users
Content-Type: application/json

{
  "name": "Alice Johnson",
  "email": "alice@example.com"
}

Response:

{
  "id": 1,
  "name": "Alice Johnson",
  "email": "alice@example.com"
}

✔ Uses 201 Created status code.
✔ Data is sent in the request body.

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✅ 2️⃣ Read (GET)

Used to retrieve data from the server.

Example: Getting all users

GET /users

Response:

[
  {
    "id": 1,
    "name": "Alice Johnson",
    "email": "alice@example.com"
  }
]

✔ Uses 200 OK status code.
✔ No request body needed.

Example: Getting a single user by ID

GET /users/1

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✅ 3️⃣ Update (PUT or PATCH)

Used to modify existing data.

• PUT: Updates all fields.
• PATCH: Updates specific fields.

Example: Updating a user with PUT

PUT /users/1
Content-Type: application/json

{
  "name": "Alice Jane Johnson",
  "email": "alice@example.com"
}

✔ Uses 200 OK status code.
✔ Replaces the entire resource.

Example: Updating only the email with PATCH

PATCH /users/1
Content-Type: application/json

{
  "email": "alice.johnson@example.com"
}

✔ Uses 200 OK status code.
✔ Modifies only the given fields.

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✅ 4️⃣ Delete (DELETE)

Used to remove a resource.

Example: Deleting a user

DELETE /users/1

Response:

{
  "message": "User deleted successfully"
}

✔ Uses 204 No Content (if no response) or 200 OK.

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📌 2. Designing CRUD Endpoints

A RESTful API follows a consistent structure:

Action	HTTP Method	Endpoint
Create a new user	POST	/users
Get all users	GET	/users
Get a user by ID	GET	/users/{id}
Update a user	PUT or PATCH	/users/{id}
Delete a user	DELETE	/users/{id}

✔ Use plural nouns (/users instead of /user).
✔ Use path parameters for specific resources (/users/{id}).
✔ Follow HTTP method conventions (GET for reading, POST for creating, etc.).

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📌 3. Implementing CRUD Operations in Express.js

Let's implement these operations using Node.js + Express.

🚀 Example: Setting Up CRUD Routes in Express.js

const express = require('express');
const app = express();
app.use(express.json()); // Middleware to parse JSON

let users = []; // Temporary in-memory database

// Create (POST) - Add a new user
app.post('/users', (req, res) => {
  const newUser = { id: users.length + 1, ...req.body };
  users.push(newUser);
  res.status(201).json(newUser);
});

// Read (GET) - Get all users
app.get('/users', (req, res) => {
  res.json(users);
});

// Read (GET) - Get a user by ID
app.get('/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  if (!user) return res.status(404).json({ error: "User not found" });
  res.json(user);
});

// Update (PUT) - Update a user
app.put('/users/:id', (req, res) => {
  let user = users.find(u => u.id === parseInt(req.params.id));
  if (!user) return res.status(404).json({ error: "User not found" });
  
  user = { ...user, ...req.body };
  res.json(user);
});

// Delete (DELETE) - Remove a user
app.delete('/users/:id', (req, res) => {
  users = users.filter(u => u.id !== parseInt(req.params.id));
  res.json({ message: "User deleted successfully" });
});

// Start the server
const PORT = 3033;
app.listen(PORT, () => console.log(`Server running on port ${PORT}`));

✔ Handles all CRUD operations.
✔ Uses status codes correctly.
✔ Includes basic error handling.

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🎯 Summary

• CRUD operations allow managing resources in an API.
• Each HTTP method maps to a CRUD action (POST -> Create, GET -> Read, etc.).
• Use structured endpoints (/users/{id}).
• Implemented a full CRUD API using Express.js.

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✅ Next Lesson: Implementing a Simple CRUD API (Hands-on Project)

In the next lesson, you’ll build a complete CRUD API with data validation and error handling. 🚀