Developer Cheat Sheets

Quick reference guides for data formats, syntax, and best practices

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📋

JSON Cheat Sheet

Basic Syntax

Object

{ "key": "value" }

Array

["item1", "item2"]

String

"text"

Number

42 or 3.14

Boolean

true or false

Null

null

Common Patterns

Nested Object

{
  "user": {
    "name": "John",
    "age": 30
  }
}

Array of Objects

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

Best Practices

✅ Use double quotes for strings

✅ No trailing commas allowed

✅ All keys must be strings

❌ No comments in JSON

❌ No undefined values

📄

YAML Cheat Sheet

Basic Syntax

Key-Value

key: value

String

name: John Doe

Number

age: 30

Boolean

active: true

Null

value: null

List

- item1
- item2
- item3

Common Patterns

Nested Object

user:
  name: John
  age: 30

List of Objects

users:
  - name: John
    age: 30
  - name: Jane
    age: 25

Multi-line String

description: |
  This is a
  multi-line string

Best Practices

✅ Use 2 spaces for indentation

✅ No tabs allowed

✅ Quote strings with special chars

✅ Use comments with #

❌ Don't mix tabs and spaces

📊

CSV Cheat Sheet

Basic Structure

Header Row

name,age,city

Data Rows

John,30,NYC
Jane,25,LA

Quoted Values

"Smith, John",30,"New York"

Empty Fields

John,,NYC

Special Cases

Comma in Value

"Smith, John",30

Quote in Value

"He said ""Hi""",30

Newline in Value

"Line 1
Line 2",30

Best Practices

✅ Always include header row

✅ Quote fields with commas

✅ Use consistent delimiters

✅ Escape quotes by doubling

❌ Avoid mixing delimiters

🔐

JWT Cheat Sheet

Structure

Format

header.payload.signature

Header Example

{
  "alg": "HS256",
  "typ": "JWT"
}

Payload Example

{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1516239022
}

Standard Claims

iss

Issuer

sub

Subject

aud

Audience

exp

Expiration Time

nbf

Not Before

iat

Issued At

jti

JWT ID

Security Tips

✅ Use HS256 or RS256 algorithms

✅ Set expiration times

✅ Validate signature on server

❌ Never store secrets in JWT

❌ Don't use "none" algorithm

🔍

Regex Cheat Sheet

Common Patterns

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

URL

https?://[^\s]+

Phone

\d{3}-\d{3}-\d{4}

IP Address

\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

Character Classes

Any digit (0-9)

Word character (a-z, A-Z, 0-9, _)

Whitespace

Any character

[abc]

Any of: a, b, or c

[^abc]

Not a, b, or c

Quantifiers

0 or more

1 or more

0 or 1

{n}

Exactly n times

{n,}

n or more times

{n,m}

Between n and m times

🌐

HTTP Status Codes

2xx Success

200

OK - Request succeeded

201

Created - Resource created

204

No Content - Success, no body

4xx Client Errors

400

Bad Request - Invalid syntax

401

Unauthorized - Auth required

403

Forbidden - No permission

404

Not Found - Resource missing

422

Unprocessable Entity - Validation failed

5xx Server Errors

500

Internal Server Error

502

Bad Gateway

503

Service Unavailable

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YAML ↔ JSON

Convert between formats