REST API

REST API is a common way for apps to communicate over HTTP.

In a REST API, the server exposes resources like users, products, or orders.

Most REST APIs send and receive JSON.

Basics

What REST Means

REST stands for Representational State Transfer.

You do not need to remember the full name.

The important idea is this:

• the URL points to a resource
• the HTTP method tells what action you want

Example:

• GET /users means get all users
• GET /users/1 means get one user
• POST /users means create a new user

Important

Use nouns in REST URLs, not verbs.

Good: /users

Avoid: /getUsers

Resources And Endpoints

A resource is the thing your API works with.

Examples:

• users
• posts
• products
• orders

An endpoint is a specific method and path together.

Examples:

• GET /users
• POST /users
• DELETE /users/1

HTTP Methods

These are the main methods you need to know:

Method	Purpose
GET	read data
POST	create new data
PUT	replace all data
PATCH	update part of data
DELETE	remove data

Simple example:

Action	Route
Get all users	GET /users
Get one user	GET /users/1
Create a user	POST /users
Update a user	PATCH /users/1
Delete a user	DELETE /users/1

Route Params And Query Params

Route Params

Use a route param when you want one specific item.

Example:

GET /users/42

Here, 42 is the user id.

Query Params

Use query params for filtering, searching, sorting, or pagination.

Examples:

• GET /users?role=admin
• GET /users?page=2
• GET /products?sort=price

Simple rule:

• route param = one item
• query param = change the list

Request And Response

When a client sends a request, it usually contains:

• a method
• a URL
• sometimes headers
• sometimes a body

Example request body:

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

Example JSON response:

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

Status Codes

Status codes tell the client what happened.

Common ones:

• 200 OK for success
• 201 Created for a new item
• 400 Bad Request for invalid input
• 401 Unauthorized when login is required
• 404 Not Found when the resource does not exist
• 500 Internal Server Error when the server fails

Small Example

app.get('/users', (req, res) => {
  res.json([
    { id: 1, name: 'Alice' },
    { id: 2, name: 'Bob' },
  ]);
});

app.post('/users', (req, res) => {
  res.status(201).json({ id: 3, name: 'Charlie' });
});

In this example:

• GET /users returns data
• POST /users creates data
• res.json() sends JSON back

Good REST Habits

• keep routes simple and predictable
• use nouns like /users and /products
• return JSON consistently
• use the correct status code
• keep request and response shapes clear