What Is a REST API?

REST stands for:

Representational State Transfer

A REST API allows:

Client ↔ Server communication

Usually using HTTP requests.

Real-World Example

Frontend application:

• Requests user data

• Sends form data

• Updates profile

• Deletes records

Backend API handles these operations.

API Communication Flow

What Are Resources?

In REST, everything is treated as a resource.

Examples:

Example Resource

We will use:

/users

HTTP Methods

REST APIs use HTTP methods to perform actions.

CRUD vs HTTP Methods

GET Request

Used to fetch data.

Example

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

GET Single User

app.get("/users/:id", (req, res) => {
  res.send(`Get user ${req.params.id}`);
});

POST Request

Used to create new data.

Example

app.post("/users", (req, res) => {
  res.send("Create user");
});

PUT Request

Used to update existing data.

Example

app.put("/users/:id", (req, res) => {
  res.send(`Update user ${req.params.id}`);
});

DELETE Request

Used to remove data.

Example

app.delete("/users/:id", (req, res) => {
  res.send(`Delete user ${req.params.id}`);
});

REST Route Structure

Why REST Route Naming Matters

Good REST APIs use clean resource-based naming.

Good Examples

/users
/products
/orders

Avoid

/getUsers
/createUser
/deleteUser

HTTP methods already describe the action.

Complete Express Example

const express = require("express");

const app = express();

app.use(express.json());

app.get("/users", (req, res) => {
  res.json([
    { id: 1, name: "Ali" },
    { id: 2, name: "Sara" }
  ]);
});

app.post("/users", (req, res) => {
  res.status(201).json({
    message: "User created"
  });
});

app.put("/users/:id", (req, res) => {
  res.json({
    message: `User ${req.params.id} updated`
  });
});

app.delete("/users/:id", (req, res) => {
  res.json({
    message: `User ${req.params.id} deleted`
  });
});

app.listen(3000);

What Is express.json()?

app.use(express.json());

Allows Express to read JSON request bodies.

Status Codes Basics

Status codes tell client what happened.

Common Status Codes

Example

res.status(201).json({
  message: "User created"
});

REST Request-Response Lifecycle

REST API Design Principles

Example API Endpoints

Common Beginner Mistakes

Using Wrong HTTP Method

Incorrect:

GET /createUser

Correct:

POST /users

Verb-Based URLs

Incorrect:

/deleteProduct

Correct:

/products/:id

with DELETE method.

Why REST Became Popular

REST APIs are:

• Simple

• Standardized

• Scalable

• Easy for frontend/backend communication

Real-World Usage

REST APIs power:

• Mobile apps

• React frontends

• SaaS platforms

• Third-party integrations

Key Takeaways

Final Notes

REST API design is one of the most important backend development skills because almost every modern application depends on APIs.

Understanding REST fundamentals makes it easier to build:

• Frontend integrations

• Mobile backends

• SaaS applications

• Scalable services