Glossary: Software Design Patterns in JavaScript

Middleware

Handlers every web request passes through, such as logging or login checks, each able to pass the request on with next() or stop it. It is chain of responsibility in web frameworks.

Where the book teaches it

Chapter 7: Behavioral patterns II: State, Template method, Chain of responsibility
Chapter 9: Patterns in modern frameworks

Related terms

Chain of responsibility Express (and Fastify, Koa, Next.js)Handler