JavaScript

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JavaScript Intermediate

The Form Validation API You Already Shipped

required, pattern and type attributes feed a full JavaScript API: custom error messages, on-your-terms timing, and async checks - without a validation library.

May 9, 2025 2 min 1,699 Read →

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JavaScript Intermediate

navigator.onLine Lies - Build Offline Detection That Doesn't

onLine only knows if there is a network interface, not whether the internet works. Real offline handling means verified checks and a retry queue for failed writes.

May 5, 2025 2 min 1,759 Read →

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JavaScript Advanced

Measure Real User Performance with PerformanceObserver

Lighthouse tells you about your machine. PerformanceObserver tells you about your users - long tasks, slow interactions and layout shifts, from the field, in a few lines.

Apr 26, 2025 2 min 1,344 Read →

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JavaScript Beginner

data-* Attributes: The Contract Between Your HTML, CSS and JS

dataset gives JavaScript typed-ish access to data attributes, CSS can select on them and even display them with attr() - one mechanism, three languages, zero coupling.

Apr 16, 2025 2 min 1,336 Read →

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JavaScript Intermediate

DocumentFragment, insertAdjacentHTML, replaceChildren: Fast DOM in 2026

innerHTML += in a loop is quadratic destruction. The platform has three precise tools for bulk DOM work, and knowing which to grab is most of the performance.

Apr 11, 2025 2 min 2,246 Read →

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JavaScript Intermediate

fetch() With a Deadline: AbortSignal.timeout and Friends

fetch waits forever by default. One static method gives every request a timeout, and combining signals cancels stale searches the moment the user keeps typing.

Apr 4, 2025 2 min 1,899 Read →

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JavaScript Intermediate

scrollIntoView Has Options (and Focus Can Skip the Scroll)

block: "center", preventScroll on focus(), the new scrollend event - the scroll-control details that make custom UI feel native instead of jumpy.

Mar 25, 2025 2 min 1,908 Read →

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JavaScript Intermediate

ResizeObserver: Components That Respond to Their Own Size

Window resize listeners cannot see a sidebar collapsing or a panel being dragged wider. ResizeObserver watches the element itself - the JS half of container-based design.

Mar 16, 2025 2 min 526 Read →

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JavaScript Intermediate

Build a "Quote This" Feature with the Selection API

That floating "tweet this quote" button on Medium-style sites is the Selection API plus one event. Here is the whole thing, popover positioning included.

Mar 7, 2025 2 min 566 Read →

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JavaScript Beginner

Stop Using Math.random() for IDs: crypto.randomUUID()

Math.random-based IDs collide more than you think and are predictable by design. The browser ships a real UUID generator and a cryptographic random source - both one-liners.

Feb 26, 2025 2 min 2,998 Read →

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JavaScript Intermediate

Your Tabs Can Talk to Each Other: BroadcastChannel

Log out in one tab, stay logged in at the other five? BroadcastChannel syncs state across tabs in three lines - and the storage event covers the legacy cases.

Feb 21, 2025 2 min 2,531 Read →

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JavaScript Intermediate

Lazy Sequences with Generators: Compute Only What You Use

Generators pause between values, which makes infinite sequences, cheap ID factories and stop-early pipelines natural - no arrays, no wasted work.

Feb 13, 2025 1 min 3,065 Read →