JavaScript

JSON stands for JavaScript Object Notation. It is a lightweight data-interchange format that is easy to read and write for humans and easy to parse and generate for machines. JSON is widely used to transmit data between a server and a client in web applications.

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✅ Why Use JSON?

• JSON is text-based and language-independent.
• It is supported by almost every programming language (including JavaScript, Python, PHP, Java, etc.).
• It’s commonly used with AJAX to exchange data with a web server.
• Easy to read, write, and modify.

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📦 JSON Syntax Rules

JSON syntax is a subset of JavaScript object syntax but is strict.

Basic Rules:

1. Data is in key/value pairs.
2. Data is separated by commas.
3. Curly braces {} hold objects.
4. Square brackets [] hold arrays.
5. Keys must be strings enclosed in double quotes " ".

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🧩 Example of JSON

{
  "name": "Alice",
  "age": 25,
  "isStudent": false,
  "skills": ["HTML", "CSS", "JavaScript"],
  "address": {
    "city": "Delhi",
    "zip": "110001"
  }
}

Breakdown:

• name, age, isStudent, skills, and address are keys.
• Their values can be:
  • String ("Alice")
  • Number (25)
  • Boolean (false)
  • Array (["HTML", "CSS", "JavaScript"])
  • Another Object ({ "city": "Delhi", "zip": "110001" })

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📤 JSON vs JavaScript Object

Although they look similar, JSON is stricter than JavaScript objects.

Feature	JSON	JavaScript Object
Keys	Must be in double quotes	Can be without quotes
Values	Strings must be in double quotes	Strings can use single or double quotes
Comments	❌ Not allowed	✅ Allowed
Functions	❌ Not allowed	✅ Allowed

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🔁 Converting Between JSON and JavaScript

JavaScript provides two methods to work with JSON:

1. JSON.parse()

Converts a JSON string to a JavaScript object.

let jsonStr = '{"name": "Alice", "age": 25}';
let obj = JSON.parse(jsonStr);
console.log(obj.name); // Output: Alice

2. JSON.stringify()

Converts a JavaScript object to a JSON string.

let person = { name: "Bob", age: 30 };
let jsonStr = JSON.stringify(person);
console.log(jsonStr); // Output: {"name":"Bob","age":30}

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🛠️ Use Cases of JSON

• API communication: Send/receive data via REST APIs.
• AJAX requests: Fetch or send data to the server without refreshing the page.
• Config files: JSON is used for storing settings (package.json, tsconfig.json).
• Storing data locally: In localStorage or sessionStorage.

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✅ Summary

• JSON is a universal data format for storing and exchanging data.
• It’s simple, lightweight, and easy to use with JavaScript.
• Use JSON.parse() to convert JSON strings to objects.
• Use JSON.stringify() to convert JavaScript objects to JSON strings.

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