JSON Syntax & Data Types

JSON has a simple syntax with just a few rules and six data types.

JSON Data Types

JSON supports exactly six data types:

1. String - Text in double quotes: "hello"
2. Number - Integer or decimal: 42, 3.14
3. Boolean - true or false
4. Null - Empty value: null
5. Array - Ordered list: [1, 2, 3]
6. Object - Key-value pairs: {"key": "value"}

Syntax Rules

• Strings must use double quotes (not single quotes)
• Keys in objects must be strings with double quotes
• No trailing commas allowed
• No comments allowed in JSON
• Numbers cannot have leading zeros

Valid vs Invalid JSON

Common Mistakes

// INVALID: single quotes
{'name': 'Alice'}

// INVALID: trailing comma
{"name": "Alice",}

// INVALID: unquoted keys
{name: "Alice"}

// INVALID: comments
{"name": "Alice"} // user name

Exercise: Identify Data Types

Exercise: Fix Invalid JSON

Key Points

• JSON has only 6 data types
• Always use double quotes for strings and keys
• No trailing commas or comments
• Numbers, booleans, and null don't need quotes