Sharique55/🔥JSON-Cheatsheet-Ultimate.md

## 🔥JSON-Cheatsheet-Ultimate.md

      
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              🔥JSON-Cheatsheet-Ultimate.md
            
          
    🚀 The Ultimate JSON Cheatsheet – Everything You Need to Know About JSON


💡 A complete JSON reference in table format: structure, data types, syntax rules, validation, and real-world applications.


Category
Subcategory
Description
Example


Basics
JSON Definition
Lightweight format for data-interchange, easy to read and write.
{ "key": "value" }


Structure
Built on key-value pairs (objects) and ordered lists (arrays).
{ "name": "John", "age": 30 }


MIME Type
MIME type for JSON is application/json.
-


Data Types
String
Text enclosed in double quotes.
"name": "John"


Number
Can be integer or floating-point.
"age": 30 or "weight": 70.5


Boolean
Supports true and false.
"isStudent": true


Null
Represents absence of value.
"middleName": null


Object
Key-value collection, wrapped in {}.
{ "name": "John", "age": 30 }


Array
Ordered list of values inside [].
"hobbies": ["reading", "coding"]


Syntax Rules
Double Quotes
Keys and string values must use double quotes.
"name": "John"


Key-Value Pair Separator
Colon : separates keys from values.
"age": 30


Comma Separation
Items separated with commas.
{ "name": "John", "age": 30 }


No Trailing Comma
Last item must not end with a comma.
✅ Correct: { "key": "val" } ❌ Incorrect: { "key": "val", }


White Spaces
Whitespace is allowed and ignored.
{ "name" : "John" , "age" : 30 }


Advanced Structures
Nested Objects
JSON objects inside other objects.
{ "user": { "name": "John" } }


Nested Arrays
Arrays within arrays.
"matrix": [[1, 2], [3, 4]]


Arrays of Objects
Array holding multiple object entries.
[{"id": 1}, {"id": 2}]


Mixed Types in Arrays
JSON array can mix data types.
[1, "text", true, null]


Encoding
Unicode
JSON supports UTF-8 and Unicode.
"symbol": "\u03C0"


Operations
Parsing
Convert JSON string to native object.
JSON.parse('{"a":1}')


Stringifying
Convert object to JSON string.
JSON.stringify({a:1})


Accessing Data
Use dot/bracket notation.
obj.name or obj["name"]


Modifying Data
Reassign value via property.
obj.name = "Doe"


Removing Data
Delete property from object.
delete obj.name


Security
JSON Injection
Sanitize inputs to prevent injection attacks.
-


Escape Characters
Escape special characters like newline (\n), tab (\t).
"message": "Line1\nLine2"


Validation
JSON Validators
Use tools like JSONLint for validation.
-


JSON Schema
Enforce structure and rules using schemas.
See: json-schema.org


Best Practices
No Comments
JSON does not support comments.
❌ // Not allowed in JSON


Consistent Keys
Use camelCase or snake_case consistently.
"firstName": "Alice"


Minified vs Pretty
Minify for storage, prettify for readability.
JSON.stringify(obj, null, 2)


Common Issues
Trailing Comma
Will break parsers.
Avoid: { "key": "val", }


Improper Quotes
Use double quotes ", not single '.
✅ "key" ❌ 'key'


Invalid Values
NaN, Infinity, and undefined are invalid.
-


Libraries
JavaScript
JSON.parse(), JSON.stringify()
-


Python
json.loads(), json.dumps()
import json


Other Languages
Use Gson (Java), Newtonsoft.Json (.NET), fastjson (Go), etc.
-


APIs & Integration
REST APIs
JSON is commonly used for request/response payloads.
Content-Type: application/json


Headers
Set header to let server know you're sending/expecting JSON.
Accept: application/json


Debugging
Browser Tools
Use DevTools → Network tab → Preview/Response.
Chrome, Firefox


Online Formatters
Tools like jsonformatter.org
-


Advanced
JSON Web Token (JWT)
Secure token format with Base64-encoded JSON parts.
header.payload.signature


JSONP
For legacy cross-domain requests using script tags.
callback({ "data": "ok" })


Protobuf (vs JSON)
JSON is human-readable; protobuf is faster and compact (used in gRPC).
-


📎 Quick Tip: Always validate your JSON before using it in your app to avoid hidden bugs! Use https://jsonlint.com or browser dev tools.
📘 Suggested Learning:

JSON Official Spec (ECMA-404)
JSON Schema Documentation


💬 "Bookmark this cheatsheet for daily JSON work. Clean, concise, and built to be your JSON best friend!"
Category	Subcategory	Description	Example
Basics	JSON Definition	Lightweight format for data-interchange, easy to read and write.	`{ "key": "value" }`
	Structure	Built on key-value pairs (objects) and ordered lists (arrays).	`{ "name": "John", "age": 30 }`
	MIME Type	MIME type for JSON is `application/json`.	-
Data Types	String	Text enclosed in double quotes.	`"name": "John"`
	Number	Can be integer or floating-point.	`"age": 30` or `"weight": 70.5`
	Boolean	Supports `true` and `false`.	`"isStudent": true`
	Null	Represents absence of value.	`"middleName": null`
	Object	Key-value collection, wrapped in `{}`.	`{ "name": "John", "age": 30 }`
	Array	Ordered list of values inside `[]`.	`"hobbies": ["reading", "coding"]`
Syntax Rules	Double Quotes	Keys and string values must use double quotes.	`"name": "John"`
	Key-Value Pair Separator	Colon `:` separates keys from values.	`"age": 30`
	Comma Separation	Items separated with commas.	`{ "name": "John", "age": 30 }`
	No Trailing Comma	Last item must not end with a comma.	✅ Correct: `{ "key": "val" }` ❌ Incorrect: `{ "key": "val", }`
	White Spaces	Whitespace is allowed and ignored.	`{ "name" : "John" , "age" : 30 }`
Advanced Structures	Nested Objects	JSON objects inside other objects.	`{ "user": { "name": "John" } }`
	Nested Arrays	Arrays within arrays.	`"matrix": [[1, 2], [3, 4]]`
	Arrays of Objects	Array holding multiple object entries.	`[{"id": 1}, {"id": 2}]`
	Mixed Types in Arrays	JSON array can mix data types.	`[1, "text", true, null]`
Encoding	Unicode	JSON supports UTF-8 and Unicode.	`"symbol": "\u03C0"`
Operations	Parsing	Convert JSON string to native object.	`JSON.parse('{"a":1}')`
	Stringifying	Convert object to JSON string.	`JSON.stringify({a:1})`
	Accessing Data	Use dot/bracket notation.	`obj.name` or `obj["name"]`
	Modifying Data	Reassign value via property.	`obj.name = "Doe"`
	Removing Data	Delete property from object.	`delete obj.name`
Security	JSON Injection	Sanitize inputs to prevent injection attacks.	-
	Escape Characters	Escape special characters like newline (`\n`), tab (`\t`).	`"message": "Line1\nLine2"`
Validation	JSON Validators	Use tools like JSONLint for validation.	-
	JSON Schema	Enforce structure and rules using schemas.	See: json-schema.org
Best Practices	No Comments	JSON does not support comments.	❌ `// Not allowed in JSON`
	Consistent Keys	Use `camelCase` or `snake_case` consistently.	`"firstName": "Alice"`
	Minified vs Pretty	Minify for storage, prettify for readability.	`JSON.stringify(obj, null, 2)`
Common Issues	Trailing Comma	Will break parsers.	Avoid: `{ "key": "val", }`
	Improper Quotes	Use double quotes `"`, not single `'`.	✅ `"key"` ❌ `'key'`
	Invalid Values	`NaN`, `Infinity`, and `undefined` are invalid.	-
Libraries	JavaScript	`JSON.parse()`, `JSON.stringify()`	-
	Python	`json.loads()`, `json.dumps()`	`import json`
	Other Languages	Use `Gson` (Java), `Newtonsoft.Json` (.NET), `fastjson` (Go), etc.	-
APIs & Integration	REST APIs	JSON is commonly used for request/response payloads.	`Content-Type: application/json`
	Headers	Set header to let server know you're sending/expecting JSON.	`Accept: application/json`
Debugging	Browser Tools	Use DevTools → Network tab → Preview/Response.	Chrome, Firefox
	Online Formatters	Tools like jsonformatter.org	-
Advanced	JSON Web Token (JWT)	Secure token format with Base64-encoded JSON parts.	`header.payload.signature`
	JSONP	For legacy cross-domain requests using script tags.	`callback({ "data": "ok" })`
	Protobuf (vs JSON)	JSON is human-readable; protobuf is faster and compact (used in gRPC).	-
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