# Typescript Best Practices

> Guide TypeScript type design, boundary validation, and type-safety reviews when implementing or changing TypeScript code.

- Skill: `shiwenbin1617/typescript-best-practices` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add shiwenbin1617/typescript-best-practices`
- Raw SKILL.md: https://api.skillmd.com/api/skills/shiwenbin1617/typescript-best-practices/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: shiwenbin1617 (https://skillmd.com/u/shiwenbin1617)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/shiwenbin1617/typescript-best-practices

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# TypeScript best practices

Follow the repository's TypeScript conventions and compiler settings. Strengthen types where they prevent a concrete invalid state or unsafe operation; avoid adding type machinery without a caller that needs it.

- Use discriminated unions for mutually exclusive states and exhaustive handling for closed variants.
- Parse external data from `unknown` at trust boundaries. Use established schemas and derive types from their authoritative definitions.
- Prefer narrowing or `satisfies` to assertions that hide a mismatch. When an assertion is unavoidable, keep it local to a verified invariant. `as const` is not an unsafe cast.
- Use branded primitives when confusing identifiers is a real risk, and non-empty collections only where an operation requires one.
- Preserve established function signatures, logging conventions, and test patterns unless the requested change requires otherwise.

Read [patterns](references/patterns.md) when a concrete example is needed. This skill does not require loading a second principle skill or running unrelated runtime tests.