REST API Basics

GET - Retrieve data
GET /api/users
GET /api/users/123

POST - Create resource
POST /api/users
Body: { "name": "John" }

PUT - Update/Replace
PUT /api/users/123

PATCH - Partial update
PATCH /api/users/123

DELETE - Remove resource
DELETE /api/users/123

2xx Success
200 OK - Request succeeded
201 Created - Resource created
204 No Content - Success, no body

4xx Client Errors
400 Bad Request
401 Unauthorized
403 Forbidden
404 Not Found

5xx Server Errors
500 Internal Server Error
503 Service Unavailable

Stateless
Each request contains all needed info

Resource-based URLs
/api/users not /api/getUsers
/api/users/123/posts

Use HTTP methods correctly
GET for reading only
POST/PUT/DELETE for changes

JSON responses
Content-Type: application/json

Express REST API
const express = require("express");
const app = express();

app.use(express.json());

// GET all users
app.get("/api/users", (req, res) => {
  res.json(users);
});

// GET single user
app.get("/api/users/:id", (req, res) => {
  const user = users.find(u => u.id === req.params.id);
  if (!user) return res.status(404).json({ error: "Not found" });
  res.json(user);
});

// POST create user
app.post("/api/users", (req, res) => {
  const newUser = req.body;
  users.push(newUser);
  res.status(201).json(newUser);
});