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Code Quality Standards

This document establishes the comprehensive code quality standards and quality assurance requirements that govern all contributions to the ts-playground project. These standards ensure consistent, maintainable, and production-ready code across all learning stages.

Code Quality Assurance Pipeline​

Linting Standards​

All code must pass comprehensive ESLint validation. The project implements a multi-layered linting approach:

Style & Formatting:

  • Consistent code patterns and structural conventions
  • Proper import/export organization
  • Naming consistency enforcement
  • Code complexity monitoring

Best Practices:

  • Detection of potential bugs and anti-patterns
  • Security vulnerability identification
  • Performance issue detection
  • TypeScript-specific error prevention

Execute linting with:

npm run lint         # Run complete linting check
npm run lint:fix     # Auto-fix fixable issues

Automated Formatting​

Code formatting follows Prettier standards with project-specific configurations:

  • Indentation: 2 spaces for TypeScript/JavaScript files
  • Line Length: 100 characters maximum
  • Semicolons: Required for consistency
  • Quotes: Single quotes for strings (except template literals)
  • Trailing Commas: Enabled for multi-line structures

Apply formatting with:

npm run format       # Format all files
npm run format:check # Verify formatting compliance

TypeScript Quality Standards​

Compilation Requirements​

  • Strict Mode: All code must compile with strict: true setting
  • No Implicit Any: Explicit typing required (noImplicitAny: true)
  • Strict Null Checks: Proper null/undefined handling (strictNullChecks: true)
  • Strict Bind Call Apply: Type-safe function method usage
  • Strict Function Types: Covariant function parameter checking

Type Safety Requirements​

  • Explicit Interfaces: Public APIs must use explicit interfaces
  • Utility Types: Leverage TypeScript's utility types for complex transformations
  • Generic Constraints: Properly constrain generic types with meaningful bounds
  • Discriminated Unions: Use for handling complex conditional types safely

Testing Quality Standards​

Test Coverage Requirements​

  • Business Logic: Minimum 80% coverage for core business logic
  • Critical Paths: 90%+ coverage for authentication, payment, and data operations
  • Overall Project: Maintain 75%+ total project coverage
  • New Features: 100% coverage required for all new functionality

Test Quality Guidelines​

  • Test-Driven Development: Implement TDD for complex business logic
  • Behavior-Driven Tests: Focus test descriptions on expected behavior rather than implementation
  • Isolation: Each test should be independent and not rely on shared state
  • Performance: Unit tests should execute quickly (aim for < 100ms per test)

Test Categories​

// Unit Tests: Isolated module/function testing
describe('UserValidator', () => {
  // Tests for validation logic in isolation
});

// Integration Tests: Module interaction testing
describe('UserService integration', () => {
  // Tests involving multiple modules working together
});

// End-to-End Tests: Full workflow testing
describe('User registration flow', () => {
  // Tests covering complete user stories
});

Performance Standards​

Performance Benchmarks​

  • API Response Time: Sub-200ms for 95% of requests under normal load
  • Memory Usage: Efficient memory management with no significant leaks
  • Startup Time: Applications should initialize within 5 seconds
  • Resource Efficiency: Optimize for both performance and resource utilization

Performance Patterns​

  • Algorithm Complexity: Choose appropriate algorithms (avoid O(n²) when O(n log n) is available)
  • Lazy Loading: Defer expensive operations until necessary
  • Caching Strategies: Implement appropriate caching levels (memory, disk, distributed)
  • Asynchronous Operations: Use async patterns appropriately to avoid blocking

Security Standards​

Input & Data Security​

  • Input Validation: Validate all external inputs using schema validation libraries
  • Output Encoding: Properly encode all dynamic content to prevent injection
  • Authentication: Implement secure authentication with proper token management
  • Authorization: Enforce proper access controls on all sensitive operations

Dependency Management​

  • Regular Updates: Keep dependencies updated to latest secure versions
  • Security Auditing: Run npm audit regularly and address all high-severity issues
  • License Compliance: Verify and maintain awareness of all dependency licenses
  • Minimized Dependencies: Only include necessary dependencies with clear purposes

Documentation Standards​

Code Documentation​

  • API Documentation: All public interfaces must have comprehensive JSDoc
  • Complex Logic: Inline documentation for non-obvious implementation decisions
  • Architecture Decisions: Document significant architectural choices in ADR files
  • Example Usage: Include practical usage examples in documentation

Commit Quality​

  • Conventional Commits: Follow conventional commit format for clear history
  • Descriptive Messages: Commits should clearly explain what and why changes were made
  • Atomic Commits: Each commit should represent a single logical change
  • Issue References: Link commits to relevant issues when applicable

Quality Metrics & Monitoring​

Continuous Integration Requirements​

  • Build Success: All code must compile without errors
  • Test Success: All tests must pass before merging
  • Lint Compliance: Code must pass all linting checks
  • Security Scanning: Automated security vulnerability detection

Quality Gates​

  • Pull Request Reviews: Minimum 1 peer review for all changes
  • Automated Checks: All CI checks must pass before merge approval
  • Documentation Updates: Changes must include appropriate documentation updates
  • Backward Compatibility: Maintain compatibility or provide migration paths

These standards ensure the ts-playground maintains professional quality throughout the learning journey, preparing developers for real-world codebase contributions.