react-day-picker/src/utils/typeguards.ts

import type {
  DateAfter,
  DateBefore,
  DateInterval,
  DateLib,
  DateRange,
  DayOfWeek
} from "../types/index.js";

/**
 * Returns true if `matcher` is of type {@link DateInterval}.
 *
 * @group Utilities
 */
export function isDateInterval(matcher: unknown): matcher is DateInterval {
  return Boolean(
    matcher &&
      typeof matcher === "object" &&
      "before" in matcher &&
      "after" in matcher
  );
}

/**
 * Returns true if `value` is a {@link DateRange} type.
 *
 * @group Utilities
 */
export function isDateRange(value: unknown): value is DateRange {
  return Boolean(value && typeof value === "object" && "from" in value);
}

/**
 * Returns true if `value` is of type {@link DateAfter}.
 *
 * @group Utilities
 */
export function isDateAfterType(value: unknown): value is DateAfter {
  return Boolean(value && typeof value === "object" && "after" in value);
}

/**
 * Returns true if `value` is of type {@link DateBefore}.
 *
 * @group Utilities
 */
export function isDateBeforeType(value: unknown): value is DateBefore {
  return Boolean(value && typeof value === "object" && "before" in value);
}

/**
 * Returns true if `value` is a {@link DayOfWeek} type.
 *
 * @group Utilities
 */
export function isDayOfWeekType(value: unknown): value is DayOfWeek {
  return Boolean(value && typeof value === "object" && "dayOfWeek" in value);
}

/** Returns true if `value` is an array of valid dates. */
export function isDatesArray(
  value: unknown,
  dateLib: DateLib
): value is Date[] {
  return Array.isArray(value) && value.every(dateLib.isDate);
}