All 164 Frontend Tutorials

Every closures tutorial gives you the same one-line definition and a counter example. This one has live demos — watch a closure's 'backpack' keep variables alive after the outer function returns, run the var-vs-let-vs-IIFE loop trap, and execute five real patterns. Plus what most tutorials skip: #private class fields as the modern alternative, WeakMap memoization for object keys, stale closures in async setInterval (not just React), the interview-question toolkit (debounce + curry + compose), and WeakRef + Symbol.dispose for closure cleanup.

Most Intersection Observer tutorials give you a fade-in-on-scroll snippet and stop. This guide adds the CSS scroll-driven animations alternative (animation-timeline: view()), content-visibility composition, IntersectionObserver v2 for ad viewability, the sticky header sentinel pattern, React useInView and Vue useIntersectionObserver hooks, Next.js/Astro SSR guards, the jsdom polyfill, an Observer family comparison, takeRecords(), and Element.checkVisibility() — plus all four classic patterns and the threshold:1 trap.

pointer-events is a one-line CSS property that controls whether an element can be the target of mouse, touch, and pen interactions. Most guides stop at click-through overlays. This guide adds the inert attribute alternative for disabled subtrees, the disabled-attribute-vs-pointer-events table for native form controls, transition-behavior: allow-discrete for fade-in menus, dialog ::backdrop click-to-close, SVG bounding-box hit areas, map/canvas HUD click-through, the JS Pointer Events API disambiguation, and the senior-dev debugging anti-pattern.

Most IndexedDB tutorials stop at hello-world and never cover what makes the difference in production: the idb library by Jake Archibald, bulk insert performance (1 transaction vs many is ~100x faster), cross-tab sync with BroadcastChannel, the Service Worker offline-first pattern, storing Files and Blobs for offline upload queues, the transaction auto-close bug that silently breaks data in Safari and Firefox, compound indexes, Dexie/RxDB/PouchDB decision, and full TypeScript typing. With a live IndexedDB playground.

Removing outline:none without a replacement is one of the most common accessibility failures on the web. CSS :focus-visible shows a focus ring for keyboard users and hides it for mouse clicks — but most tutorials stop there. This guide adds the sticky-header scroll-padding-top trap, modern inert and <dialog> focus management, the :has(:focus-visible) modern keyboard-only parent highlight, accent-color for native form focus, why tap on mobile doesn't show a focus ring, cross-browser heuristic differences, and the WICG polyfill for legacy browsers.

navigator.share looks trivial — one method, a native share sheet. But it rejects with AbortError when the user simply cancels (which most tutorials mis-handle as a failure), canShare gives false positives for unknown keys, an await before share() can break it entirely, the text+url combination produces duplicate links on WhatsApp/X, Permissions-Policy headers can block it in iframes, Next.js/Astro break at build with ReferenceError, and PWA share-target file receivers need a 303 redirect in the service worker. This guide covers all of it.

Most HTML5 video tutorials build a played-progress bar and stop. They skip the buffered bar (TimeRanges), the textTracks captions API, ::cue styling, Picture-in-Picture, the Media Session API that handles Bluetooth headphone play/pause and lock-screen artwork, the playsinline iOS bug that breaks every custom player, autoplay policy detection, codec selection with the source media attribute, MediaError handling, and the modern MediaCapabilities + requestVideoFrameCallback APIs. This guide covers all of it.

CSS @supports is pure CSS feature detection — no JavaScript, no Modernizr. The modern Modernizr alternative is built into CSS itself. This guide covers @supports examples, the not/and/or operators, the selector() function (with the empty :has() gotcha), at-rule() for detecting @layer and @scope, Tailwind's supports-[] arbitrary variant, OKLCH and View Transitions detection, @supports inside @container for component-scoped gating, the double-negation parser quirk, and the CSS.supports() JavaScript API.

Most deep-copy guides stop at structuredClone vs JSON. This update covers what every competitor skips: the structuredClone is not defined polyfill for Node 16 / Jest / jsdom, Symbol-keyed properties silently dropped, property descriptors collapsing to plain values, why Immer or Mutative is the right choice for React state (NOT structuredClone), ES2023 non-mutating array methods that replace most clone calls, concrete 1KB/100KB/1MB benchmarks, and WinterCG runtime parity across Node, Bun, Deno, and Cloudflare Workers.

How to cancel a fetch request properly — with a live search-race demo. Type fast and watch stale requests get cancelled in real time. Covers AbortController vs AbortSignal, debounce+abort for autocomplete, AbortSignal.timeout() one-liners, AbortSignal.any() composition, AbortSignal.throwIfAborted(), React useEffect cleanup, the single-use trap, custom abort reasons, memory leaks with abort listeners, and the libraries (TanStack Query, SWR, Axios, ky) that handle signals automatically.

loading=lazy looks foolproof — one attribute, defer offscreen images. But it produces no error when it fails. It silently delays your LCP if applied to the hero, does nothing on CSS backgrounds, causes layout shift without dimensions, hides images from Googlebot when paired with data-src libraries, and gets overridden silently by preload directives. Six silent failures plus WordPress auto-lazy, framework auto-lazy defaults, content-visibility, fetchpriority=low, NoScript fallback, AdSense iframes, and the picture+srcset+lazy combined pattern.

The complete CSS dark mode guide — prefers-color-scheme media query, the new light-dark() function with the color-scheme gotcha, OKLCH tokens with color-mix() for perceptual lightness scaling, Material 3 surface elevation, View Transitions API for the toggle animation, the SSR/SSG FOUC fix matrix (Next.js cookie pattern), Windows High Contrast Mode survival with forced-colors, meta theme-color for mobile chrome, Tailwind v4 @custom-variant dark, and cross-tab sync.