react-day-picker
Version:
Customizable Date Picker for React
53 lines (48 loc) • 1.41 kB
text/typescript
import { type DateLib } from "../classes/DateLib.js";
import { type DayPickerProps } from "../types/props.js";
/**
* Determines the initial month to display in the calendar based on the provided
* props.
*
* This function calculates the starting month, considering constraints such as
* `startMonth`, `endMonth`, and the number of months to display.
*
* @param props The DayPicker props, including navigation and date constraints.
* @param dateLib The date library to use for date manipulation.
* @returns The initial month to display.
*/
export function getInitialMonth(
props: Pick<
DayPickerProps,
| "fromYear"
| "toYear"
| "month"
| "defaultMonth"
| "today"
| "numberOfMonths"
| "timeZone"
>,
navStart: Date | undefined,
navEnd: Date | undefined,
dateLib: DateLib
): Date {
const {
month,
defaultMonth,
today = dateLib.today(),
numberOfMonths = 1
} = props;
let initialMonth = month || defaultMonth || today;
const { differenceInCalendarMonths, addMonths, startOfMonth } = dateLib;
if (
navEnd &&
differenceInCalendarMonths(navEnd, initialMonth) < numberOfMonths - 1
) {
const offset = -1 * (numberOfMonths - 1);
initialMonth = addMonths(navEnd, offset);
}
if (navStart && differenceInCalendarMonths(initialMonth, navStart) < 0) {
initialMonth = navStart;
}
return startOfMonth(initialMonth);
}