Web Development Roadmap

🌐 REST APIs & Routing in Express

Now you move from basic server → real backend API structure.

If you understand this topic properly, you can build production-level APIs.

🧠 What is a REST API?

REST = Representational State Transfer

Simple meaning:
👉 Backend exposes URLs
👉 Frontend sends HTTP requests
👉 Backend returns data (usually JSON)

🔥 REST API Structure

REST follows resources-based URLs.

Example resource: users

Instead of:
- /addUser
- /deleteUser

REST style:
- POST /users
- PUT /users/:id
- DELETE /users/:id

📌 HTTP Methods in REST

- GET -> Read data
- POST -> Create data
- PUT -> Update data
- DELETE -> Remove data

These map directly to CRUD.

🧩 Basic REST API Example

Step 1: Setup Express

const express = require("express");
const app = express();

app.use(express.json()); // middleware for JSON

let users = [
  { id: 1, name: "Amit" },
  { id: 2, name: "Rahul" }
];

🔍 1️⃣ GET – Fetch all users

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

➕ 2️⃣ POST – Add new user

app.post("/users", (req, res) => {
  const newUser = {
    id: users.length + 1,
    name: req.body.name
  };

  users.push(newUser);
  res.json(newUser);
});

✏️ 3️⃣ PUT – Update user

app.put("/users/:id", (req, res) => {
  const id = parseInt(req.params.id);
  const user = users.find(u => u.id === id);

  if (!user) {
    return res.status(404).json({ message: "User not found" });
  }

  user.name = req.body.name;
  res.json(user);
});

❌ 4️⃣ DELETE – Remove user

app.delete("/users/:id", (req, res) => {
  const id = parseInt(req.params.id);
  users = users.filter(u => u.id !== id);
  res.json({ message: "User deleted" });
});

▶️ Start Server

app.listen(3000, () => {
  console.log("Server running on port 3000");
});

🧠 What is Routing?

Routing means:
👉 Matching URL
👉 Matching HTTP method
👉 Running correct function

Example:
- GET /users → fetch users
- POST /users → create user

📁 Better Folder Structure (Real Projects)

project/
 ├── routes/
 │     └── userRoutes.js
 ├── controllers/
 ├── server.js

Separation of concerns = scalable backend.

⚠️ Common Beginner Mistakes

- Not using express.json()
- Not parsing req.params correctly
- Not sending status codes
- Not handling missing data

🧪 Mini Practice Task

- Create REST API for products
- GET /products
- POST /products
- PUT /products/:id
- DELETE /products/:id

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