# Common Best Practices

> Enforce SOLID principles, guard-clause style, function size limits, and intention-revealing naming across all languages. Use when refactoring for readability, applying clean-code patterns, reviewing naming conventions, or reducing function complexity.

- Skill: `hoangnguyen0403/common-best-practices` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add hoangnguyen0403/common-best-practices`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hoangnguyen0403/common-best-practices/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: HoangNguyen0403 (https://skillmd.com/u/hoangnguyen0403)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/hoangnguyen0403/common-best-practices

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# Global Best Practices

## **Priority: P0 (CRITICAL)**

## Core Principles

- **SOLID**: Follow SRP (One reason to change), OCP (Open to extension), LSP, ISP, DIP.
- **KISS/DRY/YAGNI**: Favor readability. Abstract repeated logic. No " in case" code.
- **Naming**: Use intention-revealing names (`isUserAuthenticated` > `checkUser`). Match language casing.

## Code Hygiene

- **Size Limits**: Functions < 30 lines. Services < 600 lines. Utils < 400 lines.
- **Early Returns**: Use guard clauses. Avoid deep nesting.
- **Comments**: Explain **why**, not **what**. Refactor bad code; don't comment it.
- **Input**: Validate/sanitize all external inputs.

## Anti-Patterns

- **No Hardcoded Constants**: Use named config/env vars.
- **No Deep Nesting**: Use guard clauses.
- **No Global State**: Prefer dependency injection.
- **No Empty Catches**: Always handle, log, or rethrow.

## References

- [Code Structure Patterns](references/CODE_STRUCTURE.md) — file/function organization
- [Effectiveness Guide](references/EFFECTIVENESS.md) — practical application examples