# Typescript > TypeScript coding standards and conventions including file naming rules Use when this capability is needed. - Skill: `tomevault-io/typescript-26` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/typescript-26` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/typescript-26/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/typescript-26 --- - no barrel files - avoid type assertions (`as Foo` or `as unknown as` or `Foo!`). do guards or Effect.schema stuff (ex `is`) instead - no `void` for async - use async/effect (exception [vscode-window-messages](../vscode-window-messages/SKILL.md)) - no `export *` - name exports explicitly - prefer `undefined` over null (unless server requires null) - prefer `undefined` over empty string - prefer map/filter over loops/conditionals - avoid mutation - avoid `any` - no enums or namespaces (enums compile to weird JS; use string union types instead; exception: interfaces defined outside this repo that we can't change) - no runtime errors for developer mistakes (use types to ensure exhaustive switch/case; don't throw for null/undefined when input/consumer is within our control) - .ts filenames: camelCase, no hyphens, no leading capitals - preserve comments when refactoring; remove if wrong/obsolete - exported functions: single-line jsdoc /\*_ foo _/ if name unclear; no params/return (TS provides types) - look for uses of (Object|Map).groupBy instead of older patterns --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/forcedotcom) — claim your Tome and manage your conversions.