ReddRadar
Agent skill
typescript-expert-2025
Expert TypeScript development patterns and tooling for December 2025. Use when (1) Setting up modern TypeScript projects with Bun, Node 22+, or Deno, (2) Configuring tsconfig, ESM/CJS dual publishing, or build tooling, (3) Implementing advanced type patterns like satisfies, as const, template literals, mapped types, (4) Choosing between Biome, Oxlint, or ESLint for linting, (5) Optimizing TypeScript performance, or any expert-level TypeScript architecture questions.
Stars
163
Forks
31
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/typescriptskills
SKILL.md
TypeScript Expert Guide - December 2025
Current Landscape
TypeScript Versions
| Version | Status | Key Feature |
|---|---|---|
| 5.7 | Stable | Uninitialized variable detection |
| 5.8 | Stable | --erasableSyntaxOnly, require(esm) support |
| 5.9 | Current | import defer, improved tsc --init |
| 7.0 | Preview | Go port (Strada), 10x faster type-checking |
Runtime Options
| Runtime | TS Support | Speed | Use Case |
|---|---|---|---|
| Node 22+ | Native (strip types) | Baseline | Production, ecosystem compatibility |
| Bun | Native | 3x faster | Development, all-in-one toolkit |
| Deno | Native | ~Node | Security-first, standard APIs |
| tsx | esbuild | Fast | Node + TS quick execution |
Linting Landscape
| Tool | Speed vs ESLint | Type-Aware | Notes |
|---|---|---|---|
| Biome 2.0 | 20x faster | 85% coverage | All-in-one (lint + format) |
| Oxlint 1.0 | 50-100x faster | Experimental | Linting only, 520+ rules |
| ESLint | Baseline | Full | Most customizable |
Quick Patterns
Modern tsconfig.json (TS 5.9+)
json
{
"compilerOptions": {
"target": "ESNext",
"module": "NodeNext",
"moduleResolution": "NodeNext",
"strict": true,
"noEmit": true,
"isolatedModules": true,
"esModuleInterop": true,
"skipLibCheck": true,
"declaration": true,
"declarationMap": true
}
}
Run TypeScript Directly
bash
# Node 22+ (native)
node --experimental-strip-types app.ts
# Bun (zero config)
bun app.ts
# tsx (Node + esbuild)
npx tsx app.ts
Type-Safe Object Definition
typescript
// satisfies: validate type while preserving literal inference
const config = {
port: 3000,
env: 'production',
} satisfies { port: number; env: string };
// config.env is 'production', not string
// as const: immutable literals
const routes = ['/', '/api', '/admin'] as const;
// routes[0] is '/', not string
Template Literal Types
typescript
type EventName = 'click' | 'hover' | 'scroll';
type Handler = `on${Capitalize<EventName>}`;
// 'onClick' | 'onHover' | 'onScroll'
type Route = `/api/${string}/${'get' | 'post'}`;
// '/api/users/get' | '/api/users/post' | ...
Reference Files
Load based on task:
- TS 5.5-5.9 features & TS 7 preview: See typescript-5x-features.md
- Bun, tsx, tsup, Node 22: See modern-tooling.md
- Advanced type patterns: See advanced-types.md
- Biome, Oxlint, ESLint: See linting-formatting.md
- tsconfig, package.json, ESM/CJS: See project-setup.md
- Zod, error handling, async: See runtime-patterns.md
Build Tool Quick Reference
tsup (Library Bundling)
bash
tsup src/index.ts --format esm,cjs --dts
Bun Build
bash
bun build ./src/index.ts --outdir ./dist --target node
Package Scripts
json
{
"scripts": {
"dev": "bun --watch src/index.ts",
"build": "tsup src/index.ts --format esm,cjs --dts",
"lint": "biome check .",
"typecheck": "tsc --noEmit"
}
}
Key Compiler Flags (TS 5.8+)
| Flag | Purpose |
|---|---|
--erasableSyntaxOnly |
Enforce type-strippable syntax (no enums, decorators) |
--rewriteRelativeImportExtensions |
Rewrite .ts → .js in imports |
--isolatedDeclarations |
Parallel .d.ts generation |
--noCheck |
Skip type-checking (build only) |
--verbatimModuleSyntax |
Enforce explicit type imports |
Utility Types Quick Reference
typescript
// Built-in
Partial<T> // All optional
Required<T> // All required
Readonly<T> // All readonly
Pick<T, K> // Select keys
Omit<T, K> // Exclude keys
Record<K, V> // Key-value map
Extract<T, U> // Filter union
Exclude<T, U> // Remove from union
NonNullable<T> // Remove null/undefined
ReturnType<T> // Function return type
Parameters<T> // Function parameters
Awaited<T> // Unwrap Promise
// String manipulation
Uppercase<S>
Lowercase<S>
Capitalize<S>
Uncapitalize<S>
Decision Framework
Runtime Choice
- Bun: New projects, maximum speed, all-in-one
- Node 22+: Production, ecosystem compatibility
- tsx: Existing Node projects, quick migration
Linter Choice
- Biome: New projects, speed + simplicity
- Oxlint: Speed-critical CI, existing ESLint config
- ESLint: Complex rules, full type-aware linting
Build Tool Choice
- tsup: Library publishing, ESM/CJS dual
- Bun build: Bun-native projects
- tsc: Type-checking only (use with bundler)
Didn't find tool you were looking for?