react-day-picker/src/helpers/getFormatters.ts

Customizable Date Picker for React

import * as defaultFormatters from "../formatters/index.js";
import type { DayPickerProps } from "../types/index.js";

/**
 * Merges custom formatters from the props with the default formatters.
 *
 * @param customFormatters The custom formatters provided in the DayPicker
 *   props.
 * @returns The merged formatters object.
 */
export function getFormatters(customFormatters: DayPickerProps["formatters"]) {
  if (customFormatters?.formatMonthCaption && !customFormatters.formatCaption) {
    customFormatters.formatCaption = customFormatters.formatMonthCaption;
  }
  if (
    customFormatters?.formatYearCaption &&
    !customFormatters.formatYearDropdown
  ) {
    customFormatters.formatYearDropdown = customFormatters.formatYearCaption;
  }
  return {
    ...defaultFormatters,
    ...customFormatters
  };
}