# Typescript

> TypeScript coding standards and conventions including file naming rules

- Skill: `forcedotcom/typescript-2` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add forcedotcom/typescript-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/forcedotcom/typescript-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: forcedotcom (https://skillmd.com/u/forcedotcom)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/forcedotcom/typescript-2

---


- new file copyright header: use year **2026** (e.g. `Copyright (c) 2026, salesforce.com, inc.`)
- 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)
- avoid fallbacks unless absolutely necessary — a fallback path is usually a bandaid on a bug that should be fixed upstream. Fix the root cause; don't paper over it with a default/alternate path that hides the real failure. If a fallback is genuinely required, comment why the upstream fix isn't possible.
- .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

LSP position indexing and VS Code web extension constraints: [references/lsp-and-web-extension.md](references/lsp-and-web-extension.md)