TypeScript Enterprise Architecture: Generics, Strict Typing & Utility Types

By TypeScript Core Team Alumni • Advanced • 22 min read • Updated 2026-09-13

What You Will Master in This Tutorial

Design type-safe API client wrappers using advanced generic parameters and return inferences
Eliminate runtime bugs using strict discriminated unions and exhaustive exhaustiveness checking
Leverage TypeScript 5.5+ inferred type predicates to sanitize incoming untrusted JSON data
Master utility types: ReturnType, Parameters, Omit, Pick, and custom DeepReadonly wrappers

TYPESCRIPT

type AsyncState<T> =
  | { status: 'idle' }
  | { status: 'loading' }
  | { status: 'success'; data: T }
  | { status: 'error'; error: Error };

function renderState<T>(state: AsyncState<T>): string {
  switch (state.status) {
    case 'idle':
      return 'Awaiting input...';
    case 'loading':
      return 'Fetching payload from edge...';
    case 'success':
      return `Loaded payload: ${JSON.stringify(state.data)}`;
    case 'error':
      return `Failed with exception: ${state.error.message}`;
  }
}

Frequently Asked Questions

What is the performance impact of complex TypeScript types at runtime?

Zero. TypeScript types are completely erased during the compilation step. Runtime performance is purely that of the emitted JavaScript.