The Complete JSON Guide for Developers

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data interchange format. Despite its name, JSON is language-independent and supported by virtually every programming language.

JSON Syntax Rules

JSON data is written as key/value pairs:

• Keys must be strings in double quotes
• Values can be strings, numbers, booleans, null, arrays, or objects
• No trailing commas allowed
• No comments allowed

{
  "name": "Alice",
  "age": 30,
  "active": true,
  "score": null,
  "tags": ["admin", "user"],
  "address": {
    "city": "New York",
    "zip": "10001"
  }
}

Parsing JSON in JavaScript

// Parse JSON string to object
const data = JSON.parse('{"name":"Alice","age":30}')
console.log(data.name) // "Alice"

// Convert object to JSON string
const json = JSON.stringify({ name: "Bob", age: 25 }, null, 2)

Common JSON Mistakes

1. Single quotes - JSON requires double quotes for strings
2. Trailing commas - Not allowed in JSON (but fine in JavaScript objects)
3. Undefined values - JSON doesn't support undefined; use null instead
4. Comments - JSON doesn't support comments

JSON Validation

Always validate JSON before processing:

• Use try/catch around JSON.parse()
• Consider JSON Schema for structural validation
• Use our JSON Formatter & Validator for quick validation

Best Practices

• Use consistent naming conventions (camelCase or snake_case)
• Keep nesting shallow when possible
• Use arrays for ordered collections
• Include a version field in APIs for future compatibility