Error 1: Single Quotes Instead of Double Quotes

Standard JSON forbids single quotes (`'`). All object keys and string values MUST be enclosed in double quotes (`"`).

Single Quote Error & Fix 
// ❌ INVALID (Single Quotes)
{ 'name': 'Alice', 'role': 'developer' }

// ✅ VALID (Double Quotes)
{ "name": "Alice", "role": "developer" }

Explanation: Always use double quotes around keys and strings in JSON.

Error 2: Trailing Commas in Objects or Arrays

Unlike JavaScript ES2017, trailing commas after the last array item or object property are strictly invalid in JSON specifications.

Trailing Comma Error & Fix 
// ❌ INVALID (Trailing Comma)
{
  "items": [1, 2, 3,],
  "status": "ok",
}

// ✅ VALID (No Trailing Comma)
{
  "items": [1, 2, 3],
  "status": "ok"
}

Explanation: Remove all trailing commas before closing brackets or braces.

Error 3: Unquoted Object Keys

In JavaScript object literals, key quotes can often be omitted (`{ name: "Alice" }`). In JSON, every object key must be wrapped in double quotes.

Unquoted Keys Error & Fix 
// ❌ INVALID (Unquoted Keys)
{ name: "Alice", age: 30 }

// ✅ VALID (Quoted Keys)
{ "name": "Alice", "age": 30 }

Explanation: Quote all key names with double quotes.

Error 4: Comments inside JSON Files

Standard JSON does not support single-line (`//`) or multi-line (`/* */`) comments. Including comments causes `Unexpected token /` errors during parsing.

Comment Error & Fix 
// ❌ INVALID (Comments Present)
{
  // User ID
  "id": 101
}

// ✅ VALID (Comments Stripped)
{
  "id": 101
}

Explanation: Strip all comments before parsing JSON data in standard engines.