TypeScript Development Standards

Quality Check Commands

Run these commands after every implementation:

npm run type-check        # TypeScript type checking
npm run lint              # ESLint (0 warnings required)
npm run format            # Prettier formatting
npm test                  # Run all tests
npm run test:coverage     # Coverage check (95%+ required)
npm run build             # Build verification

TypeScript Configuration

Use TypeScript 5.3+ with strict mode:

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "ESNext",
    "moduleResolution": "node",
    "strict": true,
    "esModuleInterop": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true
  }
}

Code Quality Rules

1. No any type - Use unknown with type guards
2. Strict null checks - Handle null/undefined explicitly
3. Type guards over assertions - Avoid as keyword
4. 95%+ test coverage - Required for all new code

Testing with Vitest

import { describe, it, expect } from 'vitest';

describe('myFunction', () => {
  it('should handle valid input', () => {
    expect(myFunction('input')).toBe('expected');
  });
});

ESLint Setup

{
  "extends": ["eslint:recommended", "plugin:@typescript-eslint/recommended"],
  "parser": "@typescript-eslint/parser",
  "rules": {
    "@typescript-eslint/no-unused-vars": ["error", { "argsIgnorePattern": "^_" }],
    "@typescript-eslint/no-explicit-any": "warn"
  }
}