98 lines
3.5 KiB
TypeScript
98 lines
3.5 KiB
TypeScript
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/** Returns the ISO date string (YYYY-MM-DD) of the Monday for the week containing `date`. */
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export function getWeekStart(date: Date): string {
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const d = new Date(date);
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const day = d.getDay(); // 0=Sun, 1=Mon, ...
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const diff = day === 0 ? -6 : 1 - day;
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d.setDate(d.getDate() + diff);
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return formatDate(d);
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}
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/** Adds `n` weeks to a week-start date string and returns the new week-start. */
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export function addWeeks(weekStart: string, n: number): string {
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const d = parseDate(weekStart);
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d.setDate(d.getDate() + n * 7);
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return formatDate(d);
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}
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/** Adds `n` days to a date string and returns the new date. */
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export function addDays(dateStr: string, n: number): string {
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const d = parseDate(dateStr);
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d.setDate(d.getDate() + n);
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return formatDate(d);
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}
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/** Returns an array of 7 ISO date strings for the week starting at `weekStart` (Monday). */
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export function getWeekDays(weekStart: string): string[] {
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const d = parseDate(weekStart);
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const days: string[] = [];
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for (let i = 0; i < 7; i++) {
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const day = new Date(d);
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day.setDate(d.getDate() + i);
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days.push(formatDate(day));
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}
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return days;
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}
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/** Returns a human-readable heading like "Monday, April 7th". */
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export function formatDayHeading(dateStr: string): string {
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const d = parseDate(dateStr);
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const weekday = d.toLocaleDateString(undefined, { weekday: "long" });
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const month = d.toLocaleDateString(undefined, { month: "long" });
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const day = d.getDate();
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return `${weekday}, ${month} ${ordinal(day)}`;
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}
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/** Returns a short day label like "Mon" and day number like "7". */
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export function formatShortDay(dateStr: string): { label: string; day: number } {
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const d = parseDate(dateStr);
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return {
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label: d.toLocaleDateString(undefined, { weekday: "short" }),
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day: d.getDate(),
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};
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}
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/** Returns the month + year label like "April 2026". */
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export function formatMonthYear(dateStr: string): string {
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const d = parseDate(dateStr);
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return d.toLocaleDateString(undefined, { month: "long", year: "numeric" });
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}
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/** Compact range for a Mon–Sun week, e.g. "Apr 6 – 12, 2026" or spanning two months. */
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export function formatWeekRangeLabel(weekStart: string): string {
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const start = parseDate(weekStart);
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const end = new Date(start);
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end.setDate(end.getDate() + 6);
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const sameMonth =
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start.getMonth() === end.getMonth() && start.getFullYear() === end.getFullYear();
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if (sameMonth) {
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const month = start.toLocaleDateString(undefined, { month: "short" });
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return `${month} ${start.getDate()} – ${end.getDate()}, ${start.getFullYear()}`;
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}
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return `${start.toLocaleDateString(undefined, { month: "short", day: "numeric" })} – ${end.toLocaleDateString(undefined, { month: "short", day: "numeric", year: "numeric" })}`;
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}
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/** Checks if a date string is today. */
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export function isToday(dateStr: string): boolean {
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return dateStr === formatDate(new Date());
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}
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/** Formats a Date to YYYY-MM-DD. */
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function formatDate(d: Date): string {
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const year = d.getFullYear();
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const month = String(d.getMonth() + 1).padStart(2, "0");
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const day = String(d.getDate()).padStart(2, "0");
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return `${year}-${month}-${day}`;
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}
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/** Parses a YYYY-MM-DD string to a local Date. */
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function parseDate(dateStr: string): Date {
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const parts = dateStr.split("-").map(Number);
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return new Date(parts[0]!, parts[1]! - 1, parts[2]!);
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}
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function ordinal(n: number): string {
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const s = ["th", "st", "nd", "rd"] as const;
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const v = n % 100;
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return n + (s[(v - 20) % 10] ?? s[v] ?? s[0]);
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}
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