... in the previous chapters...

A batch of genuinely useful JavaScript additions is now unflagged in Node.js 26: Set operations (union, intersection, difference), lazy iterator helpers, RegExp.escape, Promise.try, Array.fromAsync, and Float16Array. Here's each one with real, verified output.

JavaScript's broken Date object finally has a replacement. Temporal — Stage 4 in ES2026 and enabled by default in Node.js 26 — brings immutable date/time types, real time-zone support, and sane arithmetic. Here's how to use it, with examples and the polyfill for older environments.

The new HTTP QUERY method (RFC 10008, 2026) gives you the safe, idempotent, cacheable semantics of GET with the request body of POST — ideal for large or structured read operations. Here's its status, browser and server support, and a form + fetch + Node example you can actually test.

Tailwind CSS v4 is CSS-first: no tailwind.config.js, no @tailwind directives, and automatic content detection. Here's how to set it up with Vite, PostCSS, or the CLI, customize your theme with @theme, and migrate from v3.

Turn any web page into a PDF or a full-page PNG screenshot with Puppeteer and headless Chrome — natively, in just a few lines, with none of the Xvfb, DPI, or screenshot-stitching workarounds the old Nightmare approach required.

Quill internally renders both bullet and numbered lists as <ol> elements, which can break list semantics when saving content. Using getSemanticHTML() with react-quill-new ensures your exported HTML correctly distinguishes between <ul> and <ol>.

ChunkLoadError: Failed to load chunk after a deploy isn't a build cache problem. It's version skew: a tab opened before the deploy asks for a JavaScript file that the new build deleted. I reproduced it in Next.js 16.3 and tested the fixes: keeping old static files, reloading once on ChunkLoadError, what deploymentId does and doesn't do, and the CDN cache that leaves pages silently dead.

In React 19 you don't need forwardRef any more: ref is a regular prop, and useImperativeHandle lets a child expose methods like focus() or clear() to its parent. Here's the pattern in JavaScript and TypeScript, tested in Chromium, Firefox and WebKit with React 19.3, plus the StrictMode bug in the classic example, ref cleanup functions, and the key trick that often makes imperative calls unnecessary.

docker stats shows memory per container but no total. The usual one-liner sums the MEM % column, and that's wrong as soon as any container has a memory limit. In a test it reported 13.53 GiB used, 174% of the machine, when the containers were really using about 1 GB. Here's a correct shell version, a Node.js version that groups by Compose project, and what the number actually measures.

JSON.stringify(value, null, 2) pretty-prints any object without a library. Here's what the other two arguments do, which values JSON silently drops or mangles (undefined, NaN, Map, Set, Date), which ones throw (BigInt, circular references), and the newer JSON.rawJSON() for numbers too big for JavaScript. All output is real, from Node 24 and 26.

Run several Node.js containers behind nginx with Docker Compose, spread requests evenly with least_conn, and add or remove replicas without touching nginx, using the resolve option that open-source nginx gained in 1.27.3. Measured: 73 → 279 req/s going from 1 to 4 replicas, and zero failed requests while scaling down, once one easy-to-miss timeout is set. Also: why the classic Docker-DNS nginx config silently ignores its own upstream block.

Block single IPs, ranges and CIDR subnets in a Node.js or Express server with the built-in net.BlockList, without any package. The common snippet, x-forwarded-for || remoteAddress, fails twice: it never matches because Node reports ::ffff: addresses, and any client can bypass it with one header. Here's a version that works directly and behind nginx, tested on Node 24 and 26 with Express 5.