TypeScript Patterns

Production-ready patterns for building testable, type-safe, and observable TypeScript applications.

Everything starts with a simple function signature:

fn(args, deps)

• args: What varies per call (userId, input data)
• deps: Injected collaborators (database, logger, other functions)

This single pattern unlocks testability, composability, and clarity.

Where to next?

Start Learning

Begin with Testing & Testability to understand why these patterns exist and how they solve real problems.

Core Patterns

Learn the fundamental patterns: functions over classes, validation, typed errors, observability, and resilience.

Enforcement

Discover how to enforce patterns through configuration, TypeScript config, and ESLint rules.

Verification

Learn how to verify your patterns work with performance testing and validation.

The Series at a Glance

Pattern	Problem It Solves	Enforced By
Testing & Testability	Hidden dependencies	fn(args, deps) signature
Functions Over Classes	Constructor bloat	Per-function deps
Validation	Lying type signatures	Zod at the boundary
Typed Errors	Invisible failures	Result<T, E> types
Composing Workflows	Partial failures	Sagas, parallel ops
Composition Patterns	Monolithic growth	Small pieces that combine
Observability	Opaque execution	trace() wrapper
Resilience	Transient failures	step.retry() in workflows
Configuration	Bad startup state	Env schemas, fail fast
TypeScript	Type leaks	Strict compiler flags
ESLint	Pattern drift	Lint rules that fail builds
Performance	Unknown bottlenecks	Load tests + chaos tests

Bonus

• AI Coding Agents - Write effective specs for AI coding agents
• React Architecture - Framework-agnostic React patterns