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41 lines
1.4 KiB
TypeScript
41 lines
1.4 KiB
TypeScript
/**
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* A date range as the language writes it (pim-13): "2.–8. Nov. 2026" in
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* German, "Nov 2 – 8, 2026" in English, "2026年11月2日～8日" in Japanese.
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* A range glued together by hand ("2. Nov. – 8, 2026") read wrong in every
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* language but English.
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*
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* The dates are display dates (their local fields are the wall clock to
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* show), so no time zone is passed: Intl reads them in the runtime's zone,
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* as toLocaleString did.
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*/
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type RangeFormatter = Intl.DateTimeFormat & { formatRange?: (start: Date, end: Date) => string };
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/** The Intl locale for an app locale: "en" is American English in the app. */
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export function intlLocaleOf(locale: string, options?: { persianCalendar?: boolean }): string {
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const base = locale === "en" ? "en-US" : locale;
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return options?.persianCalendar ? `${base}-u-ca-persian` : base;
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}
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export function formatDateRange(
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locale: string,
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start: Date,
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end: Date,
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options: Intl.DateTimeFormatOptions,
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): string {
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let formatter: RangeFormatter;
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try {
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formatter = new Intl.DateTimeFormat(locale, options);
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} catch {
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formatter = new Intl.DateTimeFormat("en-US", options);
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}
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if (typeof formatter.formatRange === "function") {
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try {
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return formatter.formatRange(start, end);
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} catch {
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// An invalid date: fall through to the two dates.
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}
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}
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return `${formatter.format(start)} – ${formatter.format(end)}`;
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}
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