MERN — ExpressJS Fundamentals

Fundamentals

Express.js is a popular web application framework for Node.js that simplifies building web applications and APIs.

• Middleware: Functions that access the request and response objects to modify, add data, or trigger other functions.
• Router: A mini-app that only deals with routing. It can have its middleware and routing logic.
• Handler: A function that handles a specific route or endpoint.
• Error Middleware: Middleware functions that have an extra parameter for error handling.

Middleware

A request-response cycle in Express.js involves a series of middleware functions that execute sequentially. Each middleware can modify the request and response objects, end the request-response cycle, or call the next middleware in the stack.

Middleware Functions: Execute sequentially, each modifying the request/response objects or ending the request-response cycle. Examples: Logging, authentication, parsing data

const express = require('express');
const app = express();
app.use((req, res, next) => { // ( 🔴, 🔵, 🚪)…