ant-design/components/calendar/Header.tsx

import * as React from 'react';
import { GenerateConfig } from 'rc-picker/lib/generate';
import { Locale } from 'rc-picker/lib/interface';
import { useContext, useMemo } from 'react';
import { FormItemInputContext } from '../form/context';
import Select from '../select';
import { Group, Button } from '../radio';
import { CalendarMode } from './generateCalendar';

const YearSelectOffset = 10;
const YearSelectTotal = 20;

interface SharedProps<DateType> {
  prefixCls: string;
  value: DateType;
  validRange?: [DateType, DateType];
  generateConfig: GenerateConfig<DateType>;
  locale: Locale;
  fullscreen: boolean;
  divRef: React.RefObject<HTMLDivElement>;
  onChange: (year: DateType) => void;
}

function YearSelect<DateType>(props: SharedProps<DateType>) {
  const { fullscreen, validRange, generateConfig, locale, prefixCls, value, onChange, divRef } =
    props;

  const year = generateConfig.getYear(value || generateConfig.getNow());

  let start = year - YearSelectOffset;
  let end = start + YearSelectTotal;

  if (validRange) {
    start = generateConfig.getYear(validRange[0]);
    end = generateConfig.getYear(validRange[1]) + 1;
  }

  const suffix = locale && locale.year === '年' ? '年' : '';
  const options: { label: string; value: number }[] = [];
  for (let index = start; index < end; index++) {
    options.push({ label: `${index}${suffix}`, value: index });
  }

  return (
    <Select
      size={fullscreen ? undefined : 'small'}
      options={options}
      value={year}
      className={`${prefixCls}-year-select`}
      onChange={numYear => {
        let newDate = generateConfig.setYear(value, numYear);

        if (validRange) {
          const [startDate, endDate] = validRange;
          const newYear = generateConfig.getYear(newDate);
          const newMonth = generateConfig.getMonth(newDate);
          if (
            newYear === generateConfig.getYear(endDate) &&
            newMonth > generateConfig.getMonth(endDate)
          ) {
            newDate = generateConfig.setMonth(newDate, generateConfig.getMonth(endDate));
          }
          if (
            newYear === generateConfig.getYear(startDate) &&
            newMonth < generateConfig.getMonth(startDate)
          ) {
            newDate = generateConfig.setMonth(newDate, generateConfig.getMonth(startDate));
          }
        }

        onChange(newDate);
      }}
      getPopupContainer={() => divRef!.current!}
    />
  );
}

function MonthSelect<DateType>(props: SharedProps<DateType>) {