📬 HTTP Methods

📖 Definition

HTTP methods represent the actions that a client wants to perform on a server. Each method has a specific meaning and purpose, and is crucial for RESTful API design.

🎯 Understanding through Analogy

Library System

GET    = Looking through books (Retrieve)
├─ Asking the librarian "Do you have this book?"
├─ Only fetching data
└─ No change in library state

POST   = Registering a new book (Create)
├─ Adding a new book to the library
├─ Changes library state
└─ Creating a new resource

PUT    = Replacing entire book information (Full Update)
├─ Rewriting all book information
└─ Complete replacement

PATCH  = Modifying part of book information (Partial Update)
├─ Modifying only part of the book info (e.g., availability)
└─ Partial change

DELETE = Discarding a book (Delete)
├─ Removing book from library
└─ Resource deletion

💡 Main HTTP Methods

GET - Data Retrieval

Purpose: Fetch resources from the server

Characteristics:
├─ Safe: Does not change server state
├─ Idempotent: Same result on multiple calls
├─ Cacheable
└─ Remains in browser history

Request Example:
GET /api/users HTTP/1.1
Host: example.com

// JavaScript fetch API
fetch('https://api.example.com/users')
  .then(response => response.json())
  .then(data => console.log(data));

// jQuery
$.get('https://api.example.com/users', function(data) {
  console.log(data);
});

// axios
axios.get('https://api.example.com/users')
  .then(response => console.log(response.data));

# curl
curl https://api.example.com/users

# Fetch specific user
curl https://api.example.com/users/123

# Using query parameters
curl "https://api.example.com/users?page=1&limit=10"

Response Example:

HTTP/1.1 200 OK
Content-Type: application/json

{
  "users": [
    { "id": 1, "name": "John Doe" },
    { "id": 2, "name": "Jane Smith" }
  ]
}

POST - Data Creation

Purpose: Create a new resource on the server

Characteristics:
├─ Unsafe: Changes server state
├─ Not idempotent: Multiple calls create multiple resources
├─ Not cacheable
└─ Data included in request body

Request Example:
POST /api/users HTTP/1.1
Host: example.com
Content-Type: application/json

{
  "name": "John Doe",
  "email": "john@example.com"
}

// fetch API
fetch('https://api.example.com/users', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    name: 'John Doe',
    email: 'john@example.com'
  })
})
  .then(response => response.json())
  .then(data => console.log(data));

// axios
axios.post('https://api.example.com/users', {
  name: 'John Doe',
  email: 'john@example.com'
})
  .then(response => console.log(response.data));

# curl
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"John Doe","email":"john@example.com"}'

Response Example:

HTTP/1.1 201 Created
Location: /api/users/123
Content-Type: application/json

{
  "id": 123,
  "name": "John Doe",
  "email": "john@example.com",
  "createdAt": "2025-01-26T10:00:00Z"
}

PUT - Full Data Update

Purpose: Replace an entire resource with new data

Characteristics:
├─ Unsafe: Changes server state
├─ Idempotent: Same result on multiple calls
├─ Replaces entire resource
└─ Can create if not existing

Request Example:
PUT /api/users/123 HTTP/1.1
Host: example.com
Content-Type: application/json

{
  "name": "John Doe",
  "email": "newemail@example.com",
  "phone": "123-456-7890"
}

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