JavaScript has the most case variety of any mainstream language because it covers so many identifier types:

• ▸Variables and functions: camelCase — getUserById, isAuthenticated, handleButtonClick
• ▸Classes and constructor functions: PascalCase — UserService, NavigationMenu, EventEmitter
• ▸React components: PascalCase — required by React, not optional — <UserCard />, <NavMenu />
• ▸TypeScript interfaces and type aliases: PascalCase — interface UserProfile, type ApiResponse
• ▸Module-level constants (fixed values): CONSTANT_CASE — const MAX_RETRIES = 3
• ▸Enum members (TypeScript): PascalCase — enum Direction { North, South, East, West }

The Airbnb, Google, and Standard style guides all align on these conventions for JS/TS.

Python's naming conventions are formally defined in PEP 8, the official Python style guide:

• ▸Variables and functions: snake_case — user_name, get_user_by_id, calculate_total
• ▸Classes: PascalCase — UserProfile, DatabaseConnection, HttpRequestHandler
• ▸Module and file names: snake_case — user_service.py, database_config.py
• ▸Constants: CONSTANT_CASE — MAX_CONNECTIONS, DEFAULT_ENCODING
• ▸Private attributes and methods: _single_underscore prefix — self._cache
• ▸Name mangling (strong privacy): __double_underscore prefix — self.__private_data

Python is distinctive for using snake_case for virtually everything except class names, which contrasts sharply with JavaScript's mixed conventions.

Java has some of the longest-established and most rigorously followed naming conventions, formalized in the original Java Code Conventions document:

• ▸Variables and methods: camelCase — firstName, getUserById, calculateTotal
• ▸Classes and interfaces: PascalCase — UserService, Comparable, HttpRequestHandler
• ▸Constants (static final): CONSTANT_CASE — public static final int MAX_SIZE = 100
• ▸Packages: all lowercase, no separators — com.example.userservice
• ▸Generic type parameters: single uppercase letters — T, E, K, V

Java's conventions are especially strict around package names, which use all-lowercase reversed domain names as the namespace.

C# has the most PascalCase of any mainstream language — Microsoft's official guidelines extend it to nearly all public members:

• ▸Public methods, properties, classes, namespaces: PascalCase — GetUserById, UserProfile, DataService
• ▸Private fields: _camelCase with underscore prefix — _userId, _connectionString
• ▸Local variables and method parameters: camelCase — userId, connectionString
• ▸Interfaces: IPascalCase with I prefix — IDisposable, IEnumerable, IUserRepository
• ▸Constants: PascalCase (not CONSTANT_CASE, unlike most other languages) — MaxRetries, DefaultTimeout

C# is notable for using PascalCase for constants rather than CONSTANT_CASE — a convention that surprises developers coming from Java or Python.

Go uses a distinctive convention tied directly to visibility — whether something is exported (public) or unexported (private) depends entirely on whether the first letter is uppercase or lowercase:

• ▸Exported identifiers (public): PascalCase — func GetUser(), type UserProfile struct
• ▸Unexported identifiers (private): camelCase — func getUser(), type userProfile struct
• ▸Constants: PascalCase if exported, camelCase if unexported — MaxRetries vs maxRetries
• ▸Acronyms: all caps when exported — ServeHTTP not ServeHttp, parseJSON not parseJson

Go's export system makes case directly semantic: uppercase = public API, lowercase = internal detail. This is enforced by the compiler, not just convention.

Rust enforces naming conventions at the compiler level — rustc emits warnings (treated as errors in most projects) for violations:

• ▸Variables and functions: snake_case — let user_name, fn get_user_by_id()
• ▸Structs, enums, and traits: PascalCase — struct UserProfile, enum Direction, trait Display
• ▸Constants and statics: CONSTANT_CASE — const MAX_RETRIES: u32 = 3
• ▸Modules and file names: snake_case — mod user_service, user_service.rs
• ▸Enum variants: PascalCase — enum Status { Active, Inactive, Pending }

Rust is among the strictest ecosystems for naming conventions because the compiler enforces them. A Rust codebase with wrong case conventions will produce build warnings on every affected identifier.