Understanding JSON and APIs

What is JSON?

JSON (JavaScript Object Notation) is a lightweight text format for representing structured data. It’s become the standard way applications exchange data over the web.

{ "id": 101, "title": "Learn Python", "tags": ["python", "beginner"], "published": true, "author": { "name": "Asha", "id": 7 } }

JSON Rules

• Keys are always strings, wrapped in double quotes
• Values can be strings, numbers, booleans, null, arrays, or nested objects
• No trailing commas, no comments — unlike JavaScript object literals

What is an API?

An API (Application Programming Interface) is a defined way for one program to request data or actions from another. A REST API exposes data over HTTP using URLs and standard verbs.

Method	Meaning
GET	Retrieve data
POST	Create new data
PUT/PATCH	Update existing data
DELETE	Remove data

Calling an API from JavaScript

const response = await fetch("https://api.example.com/tutorials/101"); const data = await response.json(); console.log(data.title);

Parsing and Creating JSON in Code

const obj = JSON.parse('{"name": "Asha"}'); // JSON text → object const text = JSON.stringify({ name: "Asha" }); // object → JSON text

Practice Exercise

Write a JSON object representing a tutorial (title, author, tags array, published boolean), then write JavaScript to fetch it from a mock API and log just the tags.