Coding Size Limits

Coding Size Limits

Code that's too big or too nested is hard to understand. These rules keep it manageable.

Why This Matters

If code is hard for YOU to read, it's hard to fix when it breaks. Size limits are speed limits — they exist for safety.

Rules

File Size

• Sweet spot: 200-400 lines
• Maximum: 800 lines
• If a file exceeds 500 lines, consider splitting it
• Exception: auto-generated files, data files, config

Function Length

• Maximum: 50 lines
• If a function needs more, break it into named sub-steps
• A function should do ONE thing (if the name needs "and", it's too big)

Nesting Depth

• Maximum: 4 levels deep
• If you see 5+ levels of {}, extract inner logic to a function
• Early returns reduce nesting (return early, return often)

Variable Naming

• Boolean variables: start with is, has, should, can
  • isActive not active
  • hasPermission not permission
  • shouldRetry not retry
• Functions: verb + noun
  • getUser() not user()
  • validateInput() not input()
• Constants: UPPER_SNAKE_CASE
  • MAX_RETRIES not maxRetries for true constants

Immutability (CRITICAL)

• Never modify an existing object/array. Always create a new one.
• BAD: user.name = 'new'
• GOOD: const updatedUser = { ...user, name: 'new' }
• This prevents entire classes of bugs where changing one thing breaks another

Magic Numbers

• No unexplained numbers in code
• BAD: if (count > 42)
• GOOD: const MAX_ITEMS = 42; if (count > MAX_ITEMS)
• Exception: 0, 1, -1 are usually obvious

Imports

• Group imports: external libs first, then internal modules, then types
• No unused imports (clutters code, slows bundling)

Enforcement

When writing or reviewing code, check against these rules. If something violates a rule, fix it in the same change — don't leave it for later.