JSON Cheatsheet

A quick reference guide for JSON syntax, data types, and common patterns.

📝 Basic Syntax

{ }Object - key-value pairs

[ ]Array - ordered list

" "String - double quotes only

:Separates key from value

,Separates items (no trailing comma!)

🔤 Data Types

String	"hello"
Number	42, 3.14, -17, 2e10
Boolean	true, false
Null	null
Array	[1, 2, 3]
Object	{"key": "value"}

🔡 Escape Sequences

\"Quote

\\Backslash

\nNewline

\tTab

\rCarriage return

\uXXXXUnicode

🚫 Not Allowed in JSON

✗'single quotes'Use double quotes

✗// commentsNo comments

✗[1, 2, 3,]No trailing comma

✗undefinedUse null instead

✗{key: "value"}Keys must be quoted

📦 Object Example

{
  "name": "John Doe",
  "age": 30,
  "isActive": true,
  "email": null,
  "tags": ["developer", "writer"],
  "address": {
    "city": "Istanbul",
    "country": "Turkey"
  }
}

📋 Array Examples

Strings

["apple", "banana", "cherry"]

Numbers

[1, 2, 3, 4, 5]

Objects

[{"id": 1}, {"id": 2}]

Mixed

["text", 42, true, null]

💻 JavaScript Methods

JSON.parse()

// String → Object
const obj = JSON.parse('{"a":1}');
// obj.a === 1

JSON.stringify()

// Object → String
const str = JSON.stringify({a:1});
// str === '{"a":1}'

Pretty Print

JSON.stringify(obj, null, 2);
// 2-space indentation

Reviver Function

JSON.parse(str, (k, v) => {
  if (k === 'date') return new Date(v);
  return v;
});

🎯 Common Patterns

API Response

{
  "data": [...],
  "meta": {
    "total": 100,
    "page": 1
  }
}

Config File

{
  "name": "my-app",
  "version": "1.0.0",
  "scripts": {
    "build": "vite build"
  }
}

GeoJSON

{
  "type": "Point",
  "coordinates": [
    29.0, 41.0
  ]
}

Ready to work with JSON?

Format JSON → Validate JSON