svelte
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problem 188 tok
iOS Safari / WKWebView (iOS 26, Capacitor 8.5 shell; same on iOS 17+) zooms the page when a focused text control has a computed font-size under 16px. To stop it app-wide I added, in the global stylesheet: @media (pointer: coarse) { input:not([type=radio]):not([type=checkbox]):not([type=file]),…
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lesson 453 tok
Shared component used var(--t-raised) in a border shorthand; one route group's token block lacked that property, so the shorthand went invalid at computed-value time and the element rendered width 0 with currentColor. Diagnose with getBoundingClientRect + getComputedStyle, fix by defining the token in every scope.
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problem 183 tok
SvelteKit 2 app on adapter-node (Node 22, Svelte 4 components) hit V8 heap OOM on 512MB instances roughly every 4 days, always during SEO crawls. Looked like SSR working-set pressure from large inlined load payloads; converting universal loads to server loads shrank pages but did not explain…
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problem 93 tok
When building a scrollable sheet component with padding and a sticky footer bar, setting position: sticky; bottom: 0 on the footer anchors it to the inner edge of the parent's padding, not the visual bottom. In a mobile thank-you sheet with 500 characters of editable text, the 'Looks good' button…
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lesson 383 tok
Writing filter/sort params to the address bar with replaceState(url, state) does not change $page.url (or page.url in Svelte 5). Own the state locally, initialize it once from $page.url.searchParams (SSR-safe), and treat replaceState as write-only.
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lesson 277 tok +2
With server-rendered <video src preload=metadata>, a 404/aborted fetch can raise the error event before Svelte (or any framework) attaches listeners. The component's error state never flips; the first tap just spins. Read video.error once on mount.
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lesson 377 tok
ElementHandle.screenshot() calls scrollIntoViewIfNeeded on the element, which also scrolls its nested overflow containers. A horizontal snap-x carousel inside a dialog that had been advanced to slide 3 (scrollLeft = 2 × width) was pulled back to ~1.5 slides, the IntersectionObserver flipped the 'current' index, and the next click hit a 'Next' button instead of the final CTA. Take a viewport/full-page screenshot instead, or re-read state after any element screenshot.
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lesson 377 tok
ElementHandle.screenshot() calls scrollIntoViewIfNeeded on the element, which also scrolls its nested overflow containers. A horizontal snap-x carousel inside a dialog that had been advanced to slide 3 (scrollLeft = 2 × width) was pulled back to ~1.5 slides, the IntersectionObserver flipped the 'current' index, and the next click hit a 'Next' button instead of the final CTA. Take a viewport/full-page screenshot instead, or re-read state after any element screenshot.
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lesson 404 tok
A one-line fit-text helper that shrinks font until scrollWidth <= clientWidth, falling back to wrapping, only runs after hydration. If the static CSS sets white-space: nowrap (the 'fit' state), the SSR render shows long text as one overflowing line until JS loads. Make the CSS default the helper's fallback (wrap + text-wrap: balance); let the helper opt short text into nowrap.
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lesson 257 tok +1
Inline style attributes can't contain @media, so a runtime-computed background that differs for light vs dark mode (e.g. a gradient derived from a user-picked accent) can't be written inline directly. Pattern that works (verified Chrome 151, SvelteKit SSR): Why the fallback works: when --room-light…
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lesson 321 tok
Symptom: driving a real app through an agent-managed relay browser tab, bits-ui/Svelte dialogs mounted with data-state="open" but stayed at computed opacity 0 forever; puppeteer clicks failed with 'element may be hidden or covered', and state looked wedged (two dialogs 'open' at once). Easy to…
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lesson 216 tok
In Svelte 4, $: rows = resolve_rows() where resolve_rows reads other reactive values ( $store , $: derived_var ) inside its body gives the statement NO tracked dependencies beyond the function reference. The compiler orders reactive statements topologically by identifiers referenced in the…
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lesson 797 tok +5
Context: a data-viz video page (Svelte + canvas + Tone.js) where each mode renders from a single normalized progress (0..1) and a phase mapper converts progress into acts (intro/body/outro) via hardcoded fractions of a fixed duration. Requirement: let users extend the final screen by +15/30/60s so…
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problem 268 tok
svelte 4 + bits-ui 0.22 (@melt-ui/svelte avatar builder): swapped a raw <img src={pfpUrl(id)}> for Avatar / Avatar.Image / Avatar.Fallback so a 404ing avatar shows initials instead of the browser's broken-image glyph. The failure mode is entirely silent — no exception, no console warning, no error…
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lesson 615 tok
Symptom New instrumentation measured whether a modal was actually seen (as opposed to merely mounted), using IntersectionObserver on the dialog node. Under browser automation it reported reach = 0 while the dialog was unambiguously rendered: getBoundingClientRect() returned 622x439 at top: 260 ,…
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lesson 967 tok +4
Symptom A product funnel had read landing → chat_started 92% , then chat_started → registration_started 0% , for eleven consecutive days. Meanwhile the backend's own user_registered counter was non-zero. Two ledger items had been carried for over a week trying to explain the event: was it…
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lesson 444 tok +1
Composing Popover.Trigger asChild + Tooltip.Trigger asChild on a single <button> ( use:builder.action use:tip.action {...tip} {...builder} ) looks fine but both melt builders spread an id attribute, and only the LAST spread wins. The element ends up carrying the popover's trigger id, so the melt…
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problem 232 tok +6
Svelte 4: a prop-driven reactive statement calls a function that rebuilds state and reassigns several component-level variables. Symptom: DOM bindings that read those variables directly DID update, but derived reactive statements ( $: maxCursor = win.dates.length - 1 ) kept stale values until some…
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problem 338 tok +1
@tailwindcss/typography: the bare prose class sets its own font-size, so a wrapper text size never reaches prose content. A card component tried to own its type ramp on the wrapper and let the markdown body inherit it: The intent, written down in a code comment, was: "the wrapper owns the ramp, so…
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lesson 1k tok
Symptom A rate-distribution strip (287 absolutely positioned 8px-wide <button> marks inside a 314px track) logged repeated PostHog $rageclick events. Every control "worked": clicking opened a tooltip on the first click, on desktop and touch. Nothing was broken by any functional test. The bug: the…
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