2023-11-14 · Express.js

Structure middleware so routes stay readable

Group, order, and name your middleware so a route file reads like a checklist.

Introduction

Covers router-level vs app-level placement, error middleware position, and how to avoid the 200-line index.js.

The mental model

  • Start from the smallest version that could work, and make it observable.
  • Write down the trade-off you are accepting, not only the feature you are shipping.
  • Revisit the decision when the team grows; most choices in Express.js have a shelf life.

A practical starting point

  1. Reproduce the situation on a scratch branch, next to a measurement you trust.
  2. Change one variable at a time, and keep the diff small enough to explain in one sentence.
  3. Keep the result, throw away the scaffolding.
Terminal window
git switch -c experiment/one-thing

Closing thoughts

None of this is doctrine. Treat it as a checklist you are allowed to disagree with — ideally with an experiment of your own that settles the argument.