CHEGG BACKED DEV

Backend development reference

Node and Express are the runtime and HTTP framework for your API. Topics here cover bootstrapping the app, parsing JSON bodies, and structured logging—everything that runs before a route handler executes. Master this layer first so later routers and controllers plug into a consistent foundation.

Application-level middleware

Matches Application-level middleware: JSON parsing, logging, and app-wide CORS.

4 topic(s) on this page.

How to initialize an Express application — Basic

Node / Express Application-level middleware
Create the Express app instance and register core middleware before defining routes.
Learn: Every Express API starts with a single app instance. Register global middleware (JSON parsing, logging, CORS) before routes so every request is prepared the same way. Keep app.js focused on wiring; move route logic into routers as the project grows.

Supplementary examples

Minimal app with a health check

const express = require("express");
const app = express();

app.get("/health", (req, res) => res.json({ ok: true }));

const PORT = process.env.PORT || 5000;
app.listen(PORT, () => console.log(`Listening on ${PORT}`));

Register JSON parsing before routes

const express = require("express");
const app = express();

app.use(express.json()); // must run before handlers that read req.body

Course example

{
"name": "deploying-the-server",
"version": "1.0.0",
"engines": {
"node": "12.13.0"
},
"description": "",
"main": "server.js",
"scripts": {
"start": "node server",
"server": "nodemon server.js",
"client": "npm start --prefix client"
},
"keywords": [],
"dependencies": {
"express": "^4.17.1",
"cors": "^2.8.5"
},
"devDependencies": {
"nodemon": "^2.0.3"
}
}

Additional references & examples

How to add HTTP request logging — Basic

Node / Express Application-level middleware
Register pino-http (or similar) on the app to log each incoming request.
Learn: Request logging answers “what hit the server?” in production. pino-http attaches a logger to each request so handlers can log with context. Place it early in the middleware stack, after body parsers if you log POST bodies sparingly.

Supplementary examples

Attach pino-http to the app

const pinoHttp = require("pino-http");
const logger = require("./config/logger");

app.use(pinoHttp({ logger }));

Log inside a handler with req.log

async function list(req, res, next) {
  req.log.info({ path: req.path }, "listing pastes");
  // ...
}

Course example

const pinoHttp = require('pino-http')
const app = express();
app.use(pinoHttp());
app.use(cors());
app.use(express.json());
// Some code omitted for brevity

Additional references & examples

  • pino-http

    HTTP request logging integration for Express.

  • Express.js guide

    Routing, middleware order, and request/response lifecycle.

How to configure logging — Intermediate

Node / Express Application-level middleware
Centralize logger setup in a config module with log level and custom request IDs.
Learn: Centralizing logger setup avoids duplicating log level and formatting rules. Use environment variables for LOG_LEVEL in development vs production, and generate a request ID (e.g. nanoid) so log lines for one request can be correlated.

Supplementary examples

Logger module with level from env

const pino = require("pino");
const { nanoid } = require("nanoid");

module.exports = pino({
  level: process.env.LOG_LEVEL || "info",
  genReqId: () => nanoid(8),
});

Course example

const pinoHttp = require("pino-http");
const { nanoid } = require("nanoid");
const level = process.env.LOG_LEVEL
const nodeEnv = process.env.NODE_ENV || 'development'
const prettyPrint = nodeEnv === "development"
const logger = pinoHttp({
genReqId: (request) => request.headers['x-request-id'] || nanoid(),
level,
prettyPrint
});
module.exports = logger;

Additional references & examples

How to enable CORS — Basic — app-wide

Node / Express Application-level middleware
Apply the cors middleware on the Express app so all routes allow cross-origin requests.
Learn: Browsers block cross-origin API calls unless the server sends CORS headers. App-wide CORS is simplest when a single frontend origin talks to your API. Tighten options in production—avoid `origin: '*'` if cookies or credentials matter.

Supplementary examples

Default CORS for all routes

const cors = require("cors");
app.use(cors());

Restrict to one frontend origin

app.use(
  cors({
    origin: process.env.FRONTEND_URL || "http://localhost:3000",
    credentials: true,
  })
);

Course example

const logger = require("./config/logger");
const app = express();
app.use(logger);
app.use(cors());
app.use(express.json());
// Some code omitted for brevity

Additional references & examples