The Bigger Picture

We’ve worked through six patterns that form the backbone of structural design in Node.js. Each one solves a specific kind of design tension—but together, they express the same goal: to make change easy by containing it.

Here’s how they fit in the bigger picture:

• Factory: Centralizes creation and hides complexity, applying Dependency Inversion and Open/Closed so new variants plug in without touching existing code.

• Builder: Separates construction from representation, embodying Single Responsibility by keeping object creation focused, readable, and testable.

• Decorator: Extends behavior without altering core logic, representing the pure expression of Open/Closed through composition rather than modification.

• Adapter: Reconciles incompatible interfaces by blending Liskov Substitution and Dependency Inversion, allowing systems to depend on consistent contracts rather than implementations.

• Proxy: Adds control, caching, or lazy behavior while leaving core intent untouched—Single Responsibility applied dynamically at runtime.

• Strategy: Isolates algorithms behind a shared contract, combining Open/Closed and Dependency Inversion to make variation safe and predictable.

Each of these patterns provides structure for a specific type of change. Together, they form the foundation of creational and structural design—the layer where code gains clarity, composition, and flexibility.

What’s next?

Our focus has been on structure—how code is shaped to grow cleanly.