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Lesson Content

Introduction to APIs

An API (Application Programming Interface) is a set of rules and protocols that allows different software applications to communicate with each other.

What is an API?

Interface - Contract between applications
Communication - How systems exchange data
Standardization - Common format for requests/responses

Types of APIs

REST - Representational State Transfer (most common)
GraphQL - Query language for APIs
SOAP - Simple Object Access Protocol
WebSocket - Real-time bidirectional communication

API Components

Endpoint - URL where API is accessed
Method - HTTP method (GET, POST, PUT, DELETE)
Request - Data sent to API
Response - Data returned from API

Example API Call

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

// POST request
fetch('https://api.example.com/users', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ name: 'John', email: 'john@example.com' })
});

Example Code

Practice making GET and POST requests

// Simulate API calls

// GET request function
function getUsers() {
  // Simulate API response
  return Promise.resolve([
    { id: 1, name: 'Alice' },
    { id: 2, name: 'Bob' }
  ]);
}

// POST request function
function createUser(userData) {
  // Simulate API response
  return Promise.resolve({ id: 3, ...userData });
}

// Use the functions
async function main() {
  // Your code here
}

main();

Expected Output:

Users: [{id: 1, name: 'Alice'}, {id: 2, name: 'Bob'}]
Created user: {id: 3, name: 'Charlie', email: 'charlie@example.com'}

Study Tips

•Read the theory content thoroughly before practicing
•Review the example code to understand key concepts
•Proceed to the Practice tab when you're ready to code