Express code explainers

javascript

const { pool } = require('./db');
 
function withTransaction() {
  return async (req, res, next) => {

A per-request transaction middleware in Express

middleware database-transactions connection-pooling

Advanced 7 steps

javascript

const express = require('express');
const crypto = require('crypto');
const router = express.Router();

Optimistic locking with ETags in Express

optimistic-locking etag conditional-requests

Intermediate 7 steps

javascript

const express = require('express');
const router = express.Router();
 
router.get('/exports/orders', async (req, res) => {

Streaming a large JSON export in Express

streaming backpressure cursors

Advanced 9 steps

javascript

const crypto = require('crypto');
 
function idempotency({ store, ttlMs = 24 * 60 * 60 * 1000 }) {
  return async function idempotencyMiddleware(req, res, next) {

Idempotent POST requests in Express

idempotency middleware caching

Advanced 8 steps

javascript

const fs = require('fs');
const path = require('path');
const express = require('express');

Streaming video with HTTP range requests in Express

http-range-requests streaming path-traversal

Intermediate 8 steps

javascript

const { z, ZodError } = require('zod');
 
function validate(schemas) {
  return (req, res, next) => {

A reusable Zod validation middleware for Express

middleware validation schema

Intermediate 8 steps

javascript

class ProblemError extends Error {
  constructor(status, title, detail, extensions = {}) {
    super(detail || title);
    this.status = status;

RFC 7807 problem details in Express

error-handling middleware http-api

Intermediate 8 steps

javascript

const express = require('express');
const createError = require('http-errors');
const { Article } = require('../models');

Sharing route logic with router.param in Express

middleware authorization dry

Intermediate 10 steps

javascript

const express = require('express');
const cors = require('cors');
 
const app = express();

Configuring a CORS allowlist in Express

cors middleware security

Intermediate 8 steps

javascript

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

Enforcing HTTPS with Express middleware

middleware https security

Intermediate 6 steps

javascript

const express = require('express');
const router = express.Router();
 
router.get('/articles/:slug', async (req, res, next) => {

Conditional GET caching in Express

http-caching conditional-get routing

Intermediate 8 steps

javascript

const { Pool } = require('pg');
 
const pool = new Pool({
  connectionString: process.env.DATABASE_URL,

Per-request Postgres connections in Express

connection-pooling middleware transactions

Intermediate 8 steps

javascript

const express = require('express');
const router = express.Router();
const db = require('../db');

Building a paginated orders page in Express

pagination routing sql-queries

Intermediate 7 steps

javascript

const express = require('express');
const { createProxyMiddleware, fixRequestBody } = require('http-proxy-middleware');
 
const router = express.Router();

Building an API gateway proxy in Express

reverse-proxy middleware api-gateway

Intermediate 6 steps

javascript

const ROLE_PERMISSIONS = {
  admin: ['users:read', 'users:write', 'billing:read', 'billing:write'],
  manager: ['users:read', 'billing:read'],
  member: ['users:read'],

Role-based permissions middleware in Express

authorization middleware rbac

Intermediate 9 steps

javascript

const express = require('express');
const app = express();
 
app.get('/health', (req, res) => res.json({ status: 'ok' }));

Graceful shutdown in an Express server

graceful-shutdown signal-handling connection-tracking

Advanced 9 steps

javascript

const express = require('express');
const { AsyncLocalStorage } = require('async_hooks');
const { randomUUID } = require('crypto');

Per-request logging context in Express

async-local-storage middleware structured-logging

Advanced 8 steps

javascript

const express = require('express');
const cookieParser = require('cookie-parser');
 
const router = express.Router();

Remember-me login with signed cookies in Express

authentication signed-cookies sessions

Intermediate 9 steps