Building ApplicationsLesson 43Free preview

Middleware Concept

This lesson is part of Node.js · All levels

Summary

Middleware is a function that executes sequentially on each request before reaching the final handler. Each middleware receives req, res, and next so it can log, parse, validate, and authenticate. By dividing tasks into middleware chains, applications become modular and easy to test.

Key points

Middleware is added with app.use and runs in sequence
Call next() to forward the request to the next middleware
If next(error) is called, a special middleware error will handle
Express's in-house middleware includes express.json and express.static

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