Hotkeys, saved state, dates, highlighting, timers and small helpers.
The logic under the components, usable on its own.
12 parts
Single-key and modifier shortcuts, Linear style, that wait while you type and can be scoped to one part of the page.
import { useId, useRef, useState } from 'react'import { useHotkeys } from '@rchursin/product/lib/hotkeys'import { KeyCombo, TextInput } from '@rchursin/product/ui'
/** * Keys only count while focus is inside this panel (`scope`), so they never fight the rest of the * page. Single keys wait while you type in the field; mod+s has a modifier and `allowInFields`, * so it works there too (and the browser's own Save dialog stays shut). */const shortcuts = [ { combo: 'c', action: 'Create task' }, { combo: 'shift+d', action: 'Duplicate task' }, { combo: '?', action: 'Show shortcuts' }, { combo: 'mod+s', action: 'Save' }, { combo: 'esc', action: 'Clear the log' },]
let next = 0
export default function HotkeysScoped() {useState that survives a reload, stays in step across components and tabs, and never breaks when storage is blocked.
import { usePersistentState } from '@rchursin/product/lib/storage'import { Button, IconButton } from '@rchursin/product/ui'
/** * A count saved in this browser: reload the page and it is still there. The badge on the right * is a second component reading the same key, and it follows every change without props. */const KEY = 'library:hooks:reviews-today'
function ReviewCounter() { const [count, setCount, reset] = usePersistentState(KEY, 0) return ( <div className="flex flex-col gap-4"> <div className="flex items-center gap-3"> <IconButton icon="minus" label="Remove one review" variant="secondary" onClick={() => setCount((n) => Math.max(0, n - 1))} /> <output aria-live="polite" className="min-w-14 text-center text-[40px]/none font-light tracking-[-0.03em] text-fg tabular-nums"> {count} </output> <IconButton icon="plus" label="Add one review" variant="secondary" onClick={() => setCount((n) => n + 1)} /> </div>Small date maths and Intl formatting on plain Dates: month grids, week starts from the locale, ISO weeks, relative days, durations.
import { addMonths, dtf, firstDayOfWeek, formatDuration, isoWeek, relativeDay, weekdayNames } from '@rchursin/product/lib/dates'
/** * Each helper with a fixed date, Tuesday 13 October 2026 at 9:30. Names and order follow the * dates locale (en-US on this prerendered site; see setDateLocale). dtf caches one formatter per * set of options. */const day = new Date(2026, 9, 13, 9, 30)const short = dtf({ weekday: 'short', month: 'short', day: 'numeric', year: 'numeric' })
const rows = [ { call: "dtf({ weekday: 'long', month: 'long', day: 'numeric' }).format(day)", result: dtf({ weekday: 'long', month: 'long', day: 'numeric' }).format(day) }, { call: 'addMonths(new Date(2026, 0, 31), 1)', result: short.format(addMonths(new Date(2026, 0, 31), 1)) }, { call: 'firstDayOfWeek()', result: `${firstDayOfWeek()} (${weekdayNames('long')[0]})` }, { call: "weekdayNames('narrow')", result: weekdayNames('narrow').join(' ') }, { call: 'isoWeek(day)', result: String(isoWeek(day)) }, { call: 'relativeDay(new Date(2026, 9, 14), day)', result: relativeDay(new Date(2026, 9, 14), day) }, { call: 'relativeDay(new Date(2026, 9, 16), day)', result: relativeDay(new Date(2026, 9, 16), day) }, { call: 'relativeDay(new Date(2027, 1, 2), day)', result: relativeDay(new Date(2027, 1, 2), day) }, { call: 'formatDuration(3_909_000)', result: formatDuration(3_909_000) },]
export default function DateOutputs() { return ( <div className="flex w-full max-w-2xl flex-col gap-3"> <code className="font-mono text-[12px] text-fg-3">const day = new Date(2026, 9, 13, 9, 30)</code> <dl className="lux-card flex flex-col divide-y divide-line rounded-xl bg-raised"> {rows.map((r) => ( <div key={r.call} className="flex flex-col gap-1 px-4 py-2.5 sm:flex-row sm:items-baseline sm:justify-between sm:gap-6"> <dt className="min-w-0"> <code className="font-mono text-[12px]/5 break-words text-fg-2">{r.call}</code> </dt> <dd className="shrink-0 text-[13.5px] font-medium text-fg tabular-nums">{r.result}</dd> </div> ))} </dl> </div> )}Dates as "2026-10-12" strings: strict and forgiving parsers, range labels with a spoken form, and the date grid’s arrow-key model.
import { useId, useState } from 'react'import { parseISODate, parseMonth, parsePastedDate, todayISO } from '@rchursin/product/calendar/dates'import { dtf } from '@rchursin/product/lib/dates'import { Button, TextInput } from '@rchursin/product/ui'
/** * Paste or type a date. parsePastedDate is forgiving: ISO text (a time after it is fine) and * dates with a month name. It refuses all-number dates like 2/3/2026 on purpose, because * nobody can tell February 3 from March 2. parseISODate is strict: exactly YYYY-MM-DD, and a * real day (2026-02-30 is null). */const samples = ['2026-10-12', '12 Oct 2026', 'October 12, 2026', '2026-10-12T09:30', '2/3/2026', '2026-02-30']const long = dtf({ weekday: 'long', month: 'long', day: 'numeric', year: 'numeric' })
export default function PasteDate() { const id = useId() const [text, setText] = useState('12 Oct 2026') const iso = parsePastedDate(text) const strict = parseISODate(text) const monthWord = /\p{L}{3,}/u.exec(text)?.[0]A small, dependency-free syntax highlighter for TSX, TS, CSS, HTML, shell and JSON, drawn in greys, weight and tint instead of colour.
import { useId, useState } from 'react'import { tokenize, type Lang } from '@rchursin/product/lib/highlight'import { Segmented, TextInput } from '@rchursin/product/ui'
/** * tokenize() returns what the code block draws: every token with its kind. Edit the line and * watch the lexer keep JSX text, attributes and the expression inside {…} apart. */const snippets: Record<Exclude<Lang, 'html' | 'text'>, string> = { tsx: '<Button size="sm" onClick={() => save(draft)}>Save for later</Button>', ts: 'const total = runs.reduce((sum, r) => sum + r.cost, 0) // dollars', css: '.lux-card { border-radius: 16px; color: var(--rc-fg); }', bash: 'npm install --save-dev vite # dev only', json: '{ "name": "rchursin-ui", "private": true, "version": 3 }',}type Shown = keyof typeof snippets
export default function HighlightTokens() { const id = useId() const [lang, setLang] = useState<Shown>('tsx')Joins class names and skips anything falsy, so each condition sits next to the classes it adds.
import { useState } from 'react'import { cx } from '@rchursin/components/cx'import { Icon } from '@rchursin/product/icons/Icon'import { Switch } from '@rchursin/product/ui'
/** * cx joins class names and drops anything falsy, so each condition sits next to the classes it * adds. Flip the switches: the row and the class string below it change together. */export default function CxConditional() { const [selected, setSelected] = useState(true) const [done, setDone] = useState(false) const [compact, setCompact] = useState(false)
const className = cx( 'flex items-center gap-3 rounded-xl px-3 text-[13px] ring-1 ring-inset', compact ? 'h-9' : 'h-12', selected ? 'bg-selected ring-line-strong' : 'ring-line', done && 'text-fg-3 line-through', )
return ( <div className="flex w-full max-w-md flex-col gap-5"> <div className="flex flex-col gap-3"> <Switch checked={selected} onChange={setSelected} label="Selected" /> <Switch checked={done} onChange={setDone} label="Done" /> <Switch checked={compact} onChange={setCompact} label="Compact" /> </div> <div className={className}> <Icon name={done ? 'status-done' : 'status-todo'} className="size-4 shrink-0" /> <span className="min-w-0 truncate">Rotate the staging API keys</span> </div> <code className="rounded-lg bg-sunken px-3 py-2.5 font-mono text-[11.5px]/5 break-words text-fg-2">{className}</code> </div> )}Two small hooks from the calendar: a media query as a boolean, and the current time that re-renders on each whole minute or second.
import { useSyncExternalStore } from 'react'import { useMediaQuery } from '@rchursin/product/calendar/hooks'
/** * Each row is one useMediaQuery call; it re-renders when the answer changes. Resize the window * to watch the first one. The static HTML can't know your screen, so useMediaQuery answers false * until the page has hydrated; the rows show "…" until then instead of a "No" that may be wrong. */const queries = [ { query: '(min-width: 640px)', means: 'Wider than a phone' }, { query: '(prefers-color-scheme: dark)', means: 'System set to dark' }, { query: '(prefers-reduced-motion: reduce)', means: 'Reduce motion is on' }, { query: '(pointer: coarse)', means: 'Touch is the main pointer' }, { query: '(forced-colors: active)', means: 'High contrast mode' },]
const noSubscribe = () => () => {}const useHydrated = () => useSyncExternalStore( noSubscribe,Clocks that keep honest time: stopwatch and countdown hooks built on timestamps, one shared frame loop, and duration parsing.
import { useId } from 'react'import { lapText, TimeDisplay, useStopwatch } from '@rchursin/product/timer'import { Button } from '@rchursin/product/ui'
/** * A whole stopwatch in one hook. useStopwatch keeps only timestamps (when the run began, what * earlier runs banked) and saves them in this browser, so a reload or a sleeping laptop never * loses time. TimeDisplay redraws the digits; this component doesn't re-render while it runs. */export default function TinyStopwatch() { const labelId = useId() const sw = useStopwatch('library:hooks:stopwatch') const running = sw.status === 'running' const laps = [...sw.laps].reverse()
return ( <div className="flex w-full max-w-xs flex-col items-center gap-5"> <p id={labelId} className="font-mono text-[11px] tracking-[0.12em] text-fg-3 uppercase"> Test run </p>A soft two-note chime made with Web Audio: arm it inside a click, then play it later, even from a background tab.
import { useEffect, useId, useRef, useState, type CSSProperties } from 'react'import { armChime, playChime } from '@rchursin/product/timer'import { Button } from '@rchursin/product/ui'
/** * Browsers only let a page make sound after a click, so armChime() runs inside the click. After * that, playChime() can sound later on its own: "In 5 seconds" arms now and plays from a timer, * even if you switch tabs meanwhile. Two soft notes, made with Web Audio; no files to load. */type Status = 'idle' | 'ready' | 'waiting' | 'blocked'
const messages: Record<Status, string> = { idle: 'Sound is off until you press a button.', ready: 'Sound is on for this page.', waiting: 'Playing in 5 seconds.', blocked: 'This browser did not allow sound.',}
export default function ChimePlay() { const volumeId = useId()Turns a note’s Markdown into flat blocks (headings, lists, checklists, quotes) and back, so notes stay plain Markdown in storage.
import { useId, useMemo, useState } from 'react'import { parseMarkdown, serializeBlocks } from '@rchursin/product/notes'import { Textarea } from '@rchursin/product/ui'
/** * parseMarkdown turns a note into the flat blocks the editor works on; serializeBlocks writes * them back. For Markdown in the shape it writes, the round trip gives back the same text, * byte for byte. Edit the note and watch the blocks and the check below. */const initial = `# Release checklist
Ship **v2.4** on Friday.
- [x] Freeze the branch- [ ] Run the eval suite - [ ] Nightly set- [ ] Write the changelog
> Keep the rollback command handy.`
The calendar’s layout maths: overlapping events side by side, all-day bars stacked into lanes, and the sentence a screen reader hears.
import type { CalendarEvent } from '@rchursin/product/data/sample'import { calendarById, eventLabel } from '@rchursin/product/calendar/events'import { packColumns } from '@rchursin/product/calendar/layout'import { PatternFill, patternText } from '@rchursin/product/calendar/patterns'import { at, formatTimeShort } from '@rchursin/product/lib/dates'
/** * packColumns places one day's events side by side where they overlap: col, cols and span are * all a renderer needs (left = col / cols, width = span / cols). Release review starts after * the focus block ends, so it takes its column and widens into the free one next to it. * The list under the picture is what a screen reader gets, written by eventLabel. */const day = new Date(2026, 9, 13)const ev = (id: string, title: string, h: number, m: number, minutes: number, calendar: CalendarEvent['calendar']): CalendarEvent => { const start = at(day, h, m) return { id, title, start, end: new Date(start.getTime() + minutes * 60_000), calendar }}const events = [ ev('standup', 'Standup', 9, 30, 15, 'team'), ev('focus', 'Focus: fix test-fixer', 10, 0, 90, 'focus'),Copy text with a toast and a fallback when the clipboard is blocked, and save text as a file.
import { useRef, useState } from 'react'import { CopyFallback, saveTextFile, useCopy } from '@rchursin/product/iconset/copy'import { Button } from '@rchursin/product/ui'
/** * useCopy copies inside the click and confirms with a toast. When the clipboard is blocked (an * iframe without permission, an old browser), `blocked` is set: show CopyFallback, which selects * the text so Ctrl C or ⌘ C still works. saveTextFile saves the same text as a file, with its * media type. */const settings = { theme: 'system', density: 'compact', weekStartsOn: 'monday', shortcuts: true }const json = JSON.stringify(settings, null, 2)
export default function CopyAndSave() { const { copy, blocked, dismiss } = useCopy() const [saved, setSaved] = useState<string | null>(null) const copyButton = useRef<HTMLButtonElement>(null)
function closeFallback() { dismiss()Click or tab into this panel, then press a key. Outside it, nothing happens.
Reload the page: the count stays. It lives in this browser only.
const day = new Date(2026, 9, 13, 9, 30)dtf({ weekday: 'long', month: 'long', day: 'numeric' }).format(day)addMonths(new Date(2026, 0, 31), 1)firstDayOfWeek()weekdayNames('narrow')isoWeek(day)relativeDay(new Date(2026, 9, 14), day)relativeDay(new Date(2026, 9, 16), day)relativeDay(new Date(2027, 1, 2), day)formatDuration(3_909_000)flex items-center gap-3 rounded-xl px-3 text-[13px] ring-1 ring-inset h-12 bg-selected ring-line-strong(min-width: 640px)Wider than a phone(prefers-color-scheme: dark)System set to dark(prefers-reduced-motion: reduce)Reduce motion is on(pointer: coarse)Touch is the main pointer(forced-colors: active)High contrast mode