Typescript

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

Audit 0.4.1 · source sha ea59a0c53d79 · 14 Oct 2026Report an issue or request a re-scan

• Publisheralinaqi GitHub userOwner of the repository this skill is read from
• Source folderalinaqi/claude-bootstrap/skills/typescriptThe exact folder we audited
• LicenceMITAs the repository states it
• Commit pinned for this verdictea59a0c53d79A new audit runs when the source changes
• Repository statusNot archivedPushed today
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: TypeScript strict mode with eslint and jest

---
name: typescript
description: TypeScript strict mode with eslint and jest
when-to-use: When working on TypeScript files
user-invocable: false
paths: ["**/*.ts", "**/*.tsx", "tsconfig*.json"]
effort: medium
---

# TypeScript Skill


---

## Strict Mode (Non-Negotiable)

```json
// tsconfig.json
{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  }
}
```

---

## Project Structure

```
project/
├── src/
│   ├── core/               # Pure business logic
│   │   ├── types.ts        # Domain types/interfaces
│   │   ├── services/       # Pure functions
│   │   └── index.ts        # Public API
│   ├── infra/              # Side effects
│   │   ├── api/            # HTTP handlers
│   │   ├── db/             # Database operations
│   │   └── external/       # Third-party integrations
│   └── utils/              # Shared utilities
├── tests/
│   ├── unit/
│   └── integration/
├── package.json
├── tsconfig.json
└── CLAUDE.md
```

---

## Tooling (Required)

```json
// package.json scripts
{
  "scripts": {
    "lint": "eslint src/ --ext .ts,.tsx",
    "typecheck": "tsc --noEmit",
    "test": "jest",
    "test:coverage": "jest --coverage",
    "format": "prettier --write 'src/**/*.ts'"
  }
}
```

```javascript
// eslint.config.js
import eslint from '@eslint/js';
import tseslint from 'typescript-eslint';

export default tseslint.config(
  eslint.configs.recommended,
  ...tseslint.configs.strictTypeChecked,
  {
    rules: {
      '@typescript-eslint/no-explicit-any': 'error',
      '@typescript-eslint/explicit-function-return-type': 'error',
      'max-lines-per-function': ['error', 20],
      'max-depth': ['error', 2],
      'max-params': ['error', 3],
    }
  }
);
```

---

## Testing with Jest

```typescript
// tests/unit/services/user.test.ts
import { calculateTotal } from '../../../src/core/services/pricing';

describe('calculateTotal', () => {
  it('returns sum of item prices', () => {
    // Arrange
    const items = [{ price: 10 }, { price: 20 }];

    // Act
    const result = calculateTotal(items);

    // Assert
    expect(result).toBe(30);
  });

  it('returns zero for empty array', () => {
    expect(calculateTotal([])).toBe(0);
  });

  it('throws on invalid item', () => {
    expect(() => calculateTotal([{ invalid: 'item' }])).toThrow();
  });
});
```

---

## GitHub Actions

```yaml
name: TypeScript Quality Gate

on: [push, pull_request]

jobs:
  quality:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - name: Setup Node
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          
      - name: Install dependencies
        run: npm ci
        
      - name: Lint
        run: npm run lint
        
      - name: Type Check
        run: npm run typecheck
        
      - name: Test with Coverage
        run: npm run test:coverage
        
      - name: Coverage Threshold (80%)
        run: npm run test:coverage -- --coverageThreshold='{"global":{"branches":80,"functions":80,"lines":80,"statements":80}}'
```

---

## Pre-Commit Hooks

Using Husky + lint-staged:

```bash
npm install -D husky lint-staged
npx husky init
```

```json
// package.json
{
  "lint-staged": {
    "*.{ts,tsx}": [
      "eslint --fix",
      "prettier --write"
    ]
  }
}
```

```bash
# .husky/pre-commit
npx lint-staged
npx tsc --noEmit
npm run test -- --onlyChanged --passWithNoTests
```

This runs on every commit:
1. ESLint + Prettier on staged files
2. Type check entire project
3. Tests for changed files only

---

## Type Patterns

### Discriminated Unions for Results
```typescript
type Result<T> =
  | { ok: true; value: T }
  | { ok: false; error: string };

function parseUser(data: unknown): Result<User> {
  // Type-safe error handling without exceptions
}
```

### Branded Types for IDs
```typescript
type UserId = string & { readonly brand: unique symbol };
type OrderId = string & { readonly brand: unique symbol };

// Can't accidentally pass UserId where OrderId expected
function getOrder(orderId: OrderId): Order { ... }
```

### Const Assertions for Literals
```typescript
const STATUSES = ['pending', 'active', 'closed'] as const;
type Status = typeof STATUSES[number]; // 'pending' | 'active' | 'closed'
```

### Zod for Runtime Validation
```typescript
import { z } from 'zod';

const UserSchema = z.object({
  email: z.string().email(),
  name: z.string().min(1).max(100),
});

type User = z.infer<typeof UserSchema>;
```

---

## TypeScript Anti-Patterns

- ❌ `any` type - use `unknown` and narrow
- ❌ Type assertions (`as`) - use type guards
- ❌ Non-null assertions (`!`) - handle null explicitly
- ❌ `@ts-ignore` without explanation
- ❌ Enums - use const objects or union types
- ❌ Classes for data - use interfaces/types
- ❌ Default exports - use named exports

Excerpt, first 5,031 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

npm install -D husky lint-staged

git clone https://github.com/alinaqi/claude-bootstrap
git -C claude-bootstrap checkout ea59a0c53d79

Works in

1. 2026-10-14
   ✓SAFE B 89 / 100

   first audit · source ea59a0c53d79

Questions about Typescript

• github.com/alinaqi/claude-bootstrap/tree/main/skills/typescript — the audited source at commit ea59a0c53d79 and every finding aboveObserved · 14 Oct 2026

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