Variables (default)

• Selector: variable
• Allowed: camelCase, UPPER_CASE

Why This Rule

Variables follow JavaScript's standard conventions:

• camelCase: Standard for regular variables (userName, orderTotal)
• UPPER_CASE: Convention for true constants (MAX_RETRIES, API_KEY)

When to use each:

• Use camelCase for values that represent program state: let currentUser, const responseData
• Use UPPER_CASE for configuration constants and magic numbers: const MAX_ATTEMPTS = 3, const DEFAULT_TIMEOUT = 5000

This dual-format approach is nearly universal in JavaScript/TypeScript. It provides a visual cue: UPPER_CASE screams "this value never changes and represents a configuration constant," while camelCase says "this is a normal variable."

References:

• Airbnb JavaScript Style Guide - Naming Conventions
• MDN JavaScript Guide - Variables

✅ Good

let userName = 'Alice'; // WHY: camelCase for runtime variables
const MAX_RETRIES = 3; // WHY: UPPER_CASE for constants

❌ Bad

let UserName = 'Alice'; // WHY: PascalCase suggests a type or class, not a runtime variable