Learn
Cheatsheet
JSON
Syntax, types, and structure at a glance.
Value Types
| "hello" | String — always double-quoted |
| 42 / 3.14 | Number — integer or float |
| true / false | Boolean — lowercase only |
| null | Null — absence of value |
| [1, 2, 3] | Array — ordered list |
| {"k": "v"} | Object — key-value pairs |
Syntax Rules
| "key": value | Keys must be double-quoted strings |
| No trailing commas | { "a": 1 } ✅ { "a": 1, } ❌ |
| No comments | // and /* */ are not valid in JSON |
| Double quotes only | Single quotes are invalid |
Common Patterns
| {} | Empty object |
| [] | Empty array |
| [{}, {}] | Array of objects — most common API response |
| "2024-01-15" | Dates are strings — ISO 8601 recommended |