JSON Cheatsheet — The Ultimate Developer Reference

JSON (JavaScript Object Notation) is a lightweight and language-independent data-interchange format widely used in web development, APIs, and configuration files.
It allows systems to exchange structured data in a readable format, making it a universal data language across platforms.

This JSON Cheatsheet gives you a complete reference — from syntax basics to real-world examples — for developers working with JavaScript, Python, PHP, Node.js, and APIs.

What is JSON?

JSON is a text-based format for representing structured data. It uses simple syntax with key-value pairs, arrays, and nested objects.

✅ Key Benefits:

• Easy to read and write
• Lightweight and language-independent
• Compatible with most modern APIs
• Easily parsed into native data structures

Example of JSON:

{
  "name": "John Doe",
  "age": 30,
  "skills": ["HTML", "CSS", "JavaScript"],
  "active": true
}

JSON Syntax Rules

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JSON Data Types

JSON Objects and Arrays

Object Example:

{
  "id": 101,
  "title": "Developer",
  "salary": 75000
}

Array Example:

[
  "JavaScript",
  "Python",
  "PHP"
]

Array of Objects:

[
  { "id": 1, "name": "Alice" },
  { "id": 2, "name": "Bob" }
]

Nested JSON Example

{
  "student": {
    "name": "Sara",
    "grade": "A",
    "subjects": ["Math", "Science", "English"],
    "address": {
      "city": "New Delhi",
      "country": "India"
    }
  }
}

Working with JSON in JavaScript

Parsing JSON

Convert JSON string → JavaScript object:

const jsonData = '{"name": "John", "age": 25}';
const obj = JSON.parse(jsonData);
console.log(obj.name); // John

Stringify JSON

Convert JavaScript object → JSON string:

const user = { name: "Alice", age: 22 };
const jsonString = JSON.stringify(user);
console.log(jsonString);

Working with JSON in PHP

<?php
$json = '{"name":"Alice","age":22}';
$data = json_decode($json, true);  // Convert to PHP array
echo $data['name']; // Alice

$user = array("name"=>"John", "age"=>30);
echo json_encode($user);
?>

Working with JSON in Python

import json

data = '{"name": "John", "age": 30}'
parsed = json.loads(data)
print(parsed['name'])

person = {"name": "Alice", "city": "London"}
json_string = json.dumps(person)
print(json_string)

JSON in REST APIs

A typical API response in JSON:

{
  "status": "success",
  "data": {
    "id": 101,
    "title": "Learn JSON",
    "category": "Programming"
  }
}

JSON Formatting Tips

✅ Always use double quotes for keys and strings
✅ Avoid trailing commas
✅ Use online tools like phponline.in/json-formatter for clean formatting
✅ Validate JSON before using it in production

JSON vs XML

JSON Errors & Validation

Common issues:

• Missing double quotes
• Extra commas
• Unescaped characters

You can validate JSON using:

npm install -g jsonlint
jsonlint file.json

JSON Pretty Print

Format JSON for readability:

JSON.stringify(data, null, 2);

Best Practices for JSON

✅ Use lowercase keys for consistency
✅ Avoid deeply nested objects (affects performance)
✅ Keep structure consistent across APIs
✅ Include metadata like status, message, or timestamp

FAQ — JSON Cheatsheet

Q1: What is JSON used for?
JSON is used for data exchange between a client and server in web applications and APIs.

Q2: How is JSON different from JavaScript objects?
JSON is a text format, while JavaScript objects are in-memory structures.

Q3: Can JSON contain comments?
No, JSON doesn’t support comments — use metadata instead.

Q4: What tools can validate JSON?
You can use JSONLint, Postman, or online validators like json-validator.

Q5: How do I convert JSON to CSV?
You can use Python’s pandas library or online converters to transform JSON data into CSV.