# Decorator Pattern
Confidence: high
Last verified: 2026-05-22
Generation: human_only


## TL;DR

Attaches additional responsibilities dynamically, providing flexible alternative to subclassing. Decorators conform to the same interface, enabling transparent stacking.

## Core Explanation

Example: `new CompressedStream(new EncryptedStream(new FileStream()))`. Python @decorator syntax. ES7 decorators (Stage 3). React HOC (Higher-Order Components) is a decorator pattern applied to components. Middleware pattern (Express, Koa) is a variant.

## Further Reading

- [Design Patterns (Gang of Four)](undefined)