02Month-year unit value toggle — when the display-unit value switches from month to year, several years can be skipped at once

<main class="stage">
<div class="mj is-demo" id="mj">
  <div class="mj__bar">
    <button type="button" class="mj__nav" id="mjPrev" aria-label="Previous month">‹</button>
    <button type="button" class="mj__head" id="mjHead">March 2026</button>
    <button type="button" class="mj__nav" id="mjNext" aria-label="Next month">›</button>
  </div>
  <div class="mj__weekday" aria-hidden="true">
    <span>Sun</span><span>Mon</span><span>Tue</span><span>Wed</span><span>Thu</span><span>Fri</span><span>Sat</span>
  </div>
  <div class="mj__viewport" id="mjViewport">
    <div class="mj__grid" id="mjMonthGrid"></div>
  </div>
  <div class="mj__yearGrid" id="mjYearGrid"></div>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 계산 겹: slideTo() 가 뷰포트 실측 폭(getBoundingClientRect)을 슬라이드 거리로,
// 목표-현재 월 오프셋의 부호를 슬라이드 방향으로 써서 translateX 를 계산한다.
@include stage($stage-yellow);

.mj {
  width: 100%;
  max-width: 230px;
  background: $stage-paper;
  border-radius: $r-card;
  padding: $sp-2;
  box-shadow: $shadow-raised;
  box-sizing: border-box;
}

.mj__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: $sp-1;
}

.mj__nav {
  width: 20px;
  height: 20px;
  display: grid;
  place-items: center;
  border: none;
  border-radius: $r-xs;
  background: transparent;
  color: $subject-ink;
  font-size: 14px;
  cursor: pointer;
}

.mj__head {
  border: none;
  background: transparent;
  color: $subject-ink;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  padding: $sp-1 $sp-2;
  border-radius: $r-xs;
}

.mj__weekday {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  margin-bottom: $sp-1;
}

.mj__weekday span {
  font-size: 9px;
  text-align: center;
  color: rgba($subject-ink, .72);
}

.mj__viewport {
  overflow: hidden;
}

.mj__grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  grid-auto-rows: 21px;
  transition: transform $dur-base $ease-spring;
}

.mj__cell {
  display: grid;
  place-items: center;
  font-size: 11px;
  color: $subject-ink;
  border-radius: $r-xs;
}

.mj__cell--out {
  visibility: hidden;
}

.mj__yearGrid {
  display: none;
  grid-template-columns: repeat(4, 1fr);
  gap: $sp-1;
}

.mj--year .mj__weekday,
.mj--year .mj__viewport {
  display: none;
}

.mj--year .mj__yearGrid {
  display: grid;
}

.mj__ycell {
  height: 26px;
  display: grid;
  place-items: center;
  border: none;
  border-radius: $r-xs;
  background: $subject-blue;
  color: $subject-cream;
  font-size: 10px;
  cursor: pointer;
}

.mj__ycell--now {
  background: $subject-blue-deep;
}

@media (max-width: 340px) {
  .mj { max-width: 190px; }
  .mj__grid { grid-auto-rows: 17px; }
  .mj__cell { font-size: 10px; }
  .mj__ycell { height: 21px; font-size: 9px; }
  .mj__weekday span { font-size: 8px; }
}

@media (prefers-reduced-motion: reduce) {
  .mj__grid { transition: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.mj {
  width: 100%;
  max-width: 230px;
  background: #ffffff;
  border-radius: 16px;
  padding: 8px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  box-sizing: border-box;
}

.mj__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 4px;
}

.mj__nav {
  width: 20px;
  height: 20px;
  display: grid;
  place-items: center;
  border: none;
  border-radius: 4px;
  background: transparent;
  color: #17141a;
  font-size: 14px;
  cursor: pointer;
}

.mj__head {
  border: none;
  background: transparent;
  color: #17141a;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 4px;
}

.mj__weekday {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  margin-bottom: 4px;
}

.mj__weekday span {
  font-size: 9px;
  text-align: center;
  color: rgba(23, 20, 26, 0.72);
}

.mj__viewport {
  overflow: hidden;
}

.mj__grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  grid-auto-rows: 21px;
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.mj__cell {
  display: grid;
  place-items: center;
  font-size: 11px;
  color: #17141a;
  border-radius: 4px;
}

.mj__cell--out {
  visibility: hidden;
}

.mj__yearGrid {
  display: none;
  grid-template-columns: repeat(4, 1fr);
  gap: 4px;
}

.mj--year .mj__weekday,
.mj--year .mj__viewport {
  display: none;
}

.mj--year .mj__yearGrid {
  display: grid;
}

.mj__ycell {
  height: 26px;
  display: grid;
  place-items: center;
  border: none;
  border-radius: 4px;
  background: #2f6df6;
  color: #fff7e6;
  font-size: 10px;
  cursor: pointer;
}

.mj__ycell--now {
  background: #0a4fe8;
}

@media (max-width: 340px) {
  .mj {
    max-width: 190px;
  }
  .mj__grid {
    grid-auto-rows: 17px;
  }
  .mj__cell {
    font-size: 10px;
  }
  .mj__ycell {
    height: 21px;
    font-size: 9px;
  }
  .mj__weekday span {
    font-size: 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .mj__grid {
    transition: none;
  }
}

(function () {
  var YEAR = 2026; // 계산 겹 상수: 연도 고정, new Date() 미사용
  var MONTH_LABEL = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
  var HEADER_LABEL = [
    'January 2026', 'February 2026', 'March 2026', 'April 2026', 'May 2026', 'June 2026',
    'July 2026', 'August 2026', 'September 2026', 'October 2026', 'November 2026', 'December 2026'
  ];
  var AUTO_SEQ = [3, 7, 11, 3]; // 계산 겹: 자동재생이 도는 목표 Mon 순서, 오프셋 부호로 슬라이드 방향을 정한다
  var CELL_TOTAL = 42; // 계산 겹: 6행 고정 — 월마다 칸 수가 달라도 뷰포트 높이가 흔들리지 않는다

  function isLeap(y) { return (y % 4 === 0 && y % 100 !== 0) || y % 400 === 0; }
  function daysInMonth(y, m) {
    var t = [31, isLeap(y) ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
    return t[m - 1];
  }
  function dow(y, m, d) { // Zeller 합동식 — 0=Sun ~ 6=Sat
    var yy = y, mm = m;
    if (mm < 3) { yy -= 1; mm += 12; }
    var K = yy % 100, J = Math.floor(yy / 100);
    var h = (d + Math.floor(13 * (mm + 1) / 5) + K + Math.floor(K / 4) + Math.floor(J / 4) - 2 * J) % 7;
    h = ((h % 7) + 7) % 7;
    return (h + 6) % 7;
  }

  var root = document.getElementById('mj');
  var head = document.getElementById('mjHead');
  var prevBtn = document.getElementById('mjPrev');
  var nextBtn = document.getElementById('mjNext');
  var viewport = document.getElementById('mjViewport');
  var monthGrid = document.getElementById('mjMonthGrid');
  var yearGrid = document.getElementById('mjYearGrid');

  var current = 3;
  var mode = 'month';

  function renderMonth(m) {
    monthGrid.innerHTML = '';
    var n = daysInMonth(YEAR, m);
    var lead = dow(YEAR, m, 1);
    var trail = CELL_TOTAL - lead - n;
    var i, cell;
    for (i = 0; i < lead; i++) {
      cell = document.createElement('span');
      cell.className = 'mj__cell mj__cell--out';
      monthGrid.appendChild(cell);
    }
    for (var d = 1; d <= n; d++) {
      cell = document.createElement('span');
      cell.className = 'mj__cell';
      cell.textContent = String(d);
      monthGrid.appendChild(cell);
    }
    for (i = 0; i < trail; i++) {
      cell = document.createElement('span');
      cell.className = 'mj__cell mj__cell--out';
      monthGrid.appendChild(cell);
    }
  }

  function renderYear(highlight) {
    yearGrid.innerHTML = '';
    for (var i = 0; i < 12; i++) {
      var btn = document.createElement('button');
      btn.type = 'button';
      btn.className = 'mj__ycell' + (i + 1 === highlight ? ' mj__ycell--now' : '');
      btn.textContent = MONTH_LABEL[i];
      btn.dataset.m = String(i + 1);
      btn.addEventListener('click', function (e) {
        human();
        slideTo(parseInt(e.currentTarget.dataset.m, 10));
      });
      yearGrid.appendChild(btn);
    }
  }

  function setHead(m) { head.textContent = HEADER_LABEL[m - 1]; }

  function slideTo(target) {
    // 계산 겹: 뷰포트 실측 폭을 슬라이드 거리로, 목표-현재 오프셋 부호를 슬라이드 방향으로 쓴다
    var dist = viewport.getBoundingClientRect().width;
    var dir = target >= current ? 1 : -1;
    current = target;
    renderMonth(current);
    setHead(current);
    root.classList.remove('mj--year');
    mode = 'month';
    monthGrid.style.transition = 'none';
    monthGrid.style.transform = 'translateX(' + (dir * dist) + 'px)';
    void monthGrid.offsetWidth;
    monthGrid.style.transition = '';
    monthGrid.style.transform = 'translateX(0)';
  }

  function stepMonth(delta) {
    var target = current + delta;
    if (target < 1) target = 12;
    if (target > 12) target = 1;
    slideTo(target);
  }

  function toggleYear() {
    mode = mode === 'year' ? 'month' : 'year';
    root.classList.toggle('mj--year', mode === 'year');
    if (mode === 'year') renderYear(current);
  }

  function human() {
    root.classList.remove('is-demo');
    stopAutoplay();
  }
  head.addEventListener('click', function () { human(); toggleYear(); });
  prevBtn.addEventListener('click', function () { human(); stepMonth(-1); });
  nextBtn.addEventListener('click', function () { human(); stepMonth(1); });
  document.addEventListener('keydown', function (e) {
    if (e.key === 'ArrowLeft') { human(); stepMonth(-1); }
    if (e.key === 'ArrowRight') { human(); stepMonth(1); }
  });

  var seqIdx = 0;
  var autoTimer = null;
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  function tick() {
    // 자동재생은 슬라이드(transform 트랜지션)만 반복한다 — 연·Mon 전환 자체는
    // display 즉시 전환이라 캡처 프레임에 순간 컷으로만 찍혀 움직인 프레임이 안 는다.
    seqIdx = (seqIdx + 1) % AUTO_SEQ.length;
    slideTo(AUTO_SEQ[seqIdx]);
  }

  renderMonth(current);
  setHead(current);
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(tick, 480); }
})();

import { useEffect, useRef, useState } from 'react';
import styles from './DatePickerMonthYearJump.module.scss';

type Box<T> = { current: T };

const YEAR = 2026; // 계산 겹 상수: 연도 고정, new Date() 미사용
const MONTH_LABEL = ['1월', '2월', '3월', '4월', '5월', '6월', '7월', '8월', '9월', '10월', '11월', '12월'];
const HEADER_LABEL = [
  '2026년 1월', '2026년 2월', '2026년 3월', '2026년 4월', '2026년 5월', '2026년 6월',
  '2026년 7월', '2026년 8월', '2026년 9월', '2026년 10월', '2026년 11월', '2026년 12월',
];
const AUTO_SEQ = [3, 7, 11, 3]; // 계산 겹: 자동재생이 도는 목표 월 순서, 오프셋 부호로 슬라이드 방향을 정한다
const CELL_TOTAL = 42; // 계산 겹: 6행 고정 — 월마다 칸 수가 달라도 뷰포트 높이가 흔들리지 않는다

function isLeap(y: number) {
  return (y % 4 === 0 && y % 100 !== 0) || y % 400 === 0;
}

function daysInMonth(y: number, m: number) {
  const t = [31, isLeap(y) ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
  return t[m - 1];
}

function dow(y: number, m: number, d: number) { // Zeller 합동식 — 0=일 ~ 6=토
  let yy = y;
  let mm = m;
  if (mm < 3) { yy -= 1; mm += 12; }
  const K = yy % 100;
  const J = Math.floor(yy / 100);
  let h = (d + Math.floor((13 * (mm + 1)) / 5) + K + Math.floor(K / 4) + Math.floor(J / 4) - 2 * J) % 7;
  h = ((h % 7) + 7) % 7;
  return (h + 6) % 7;
}

function buildCells(m: number) {
  const n = daysInMonth(YEAR, m);
  const lead = dow(YEAR, m, 1);
  const trail = CELL_TOTAL - lead - n;
  const cells: { key: string; d: number | null }[] = [];
  for (let i = 0; i < lead; i++) cells.push({ key: 'l' + i, d: null });
  for (let d = 1; d <= n; d++) cells.push({ key: 'd' + d, d });
  for (let i = 0; i < trail; i++) cells.push({ key: 't' + i, d: null });
  return cells;
}

const WEEKDAY = ['일', '월', '화', '수', '목', '금', '토'];

export default function DatePickerMonthYearJump() {
  const viewportRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const gridRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const [isDemo, setIsDemo] = useState(true);
  const [mode, setMode] = useState<'month' | 'year'>('month');
  const [current, setCurrent] = useState(3);
  const seqIdxRef = useRef(0) as unknown as Box<number>;

  function human() {
    setIsDemo(false);
  }

  function slideTo(target: number) {
    // 계산 겹: 뷰포트 실측 폭을 슬라이드 거리로, 목표-현재 월 오프셋 부호를 슬라이드 방향으로 쓴다
    const viewport = viewportRef.current;
    const grid = gridRef.current;
    if (!viewport || !grid) { setCurrent(target); setMode('month'); return; }
    const dist = viewport.getBoundingClientRect().width;
    const dir = target >= current ? 1 : -1;
    setCurrent(target);
    setMode('month');
    grid.style.transition = 'none';
    grid.style.transform = 'translateX(' + dir * dist + 'px)';
    void grid.offsetWidth;
    grid.style.transition = '';
    grid.style.transform = 'translateX(0)';
  }

  function stepMonth(delta: number) {
    let target = current + delta;
    if (target < 1) target = 12;
    if (target > 12) target = 1;
    slideTo(target);
  }

  useEffect(() => {
    function onKey(e: KeyboardEvent) {
      if (e.key === 'ArrowLeft') { human(); stepMonth(-1); }
      if (e.key === 'ArrowRight') { human(); stepMonth(1); }
    }
    document.addEventListener('keydown', onKey);
    return () => document.removeEventListener('keydown', onKey);
  });

  useEffect(() => {
    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    if (!isDemo || reduce) return;
    const timer = window.setInterval(() => {
      seqIdxRef.current = (seqIdxRef.current + 1) % AUTO_SEQ.length;
      slideTo(AUTO_SEQ[seqIdxRef.current]);
    }, 480);
    return () => window.clearInterval(timer);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [isDemo]);

  const cells = buildCells(current);

  return (
    <div className={`${styles.mj} ${isDemo ? styles.isDemo : ''} ${mode === 'year' ? styles.mjYear : ''}`}>
      <div className={styles.mjBar}>
        <button type="button" className={styles.mjNav} aria-label="이전 달" onClick={() => { human(); stepMonth(-1); }}>‹</button>
        <button
          type="button"
          className={styles.mjHead}
          onClick={() => { human(); setMode((v) => (v === 'year' ? 'month' : 'year')); }}
        >
          {HEADER_LABEL[current - 1]}
        </button>
        <button type="button" className={styles.mjNav} aria-label="다음 달" onClick={() => { human(); stepMonth(1); }}>›</button>
      </div>
      <div className={styles.mjWeekday} aria-hidden="true">
        {WEEKDAY.map((w) => <span key={w}>{w}</span>)}
      </div>
      <div className={styles.mjViewport} ref={viewportRef}>
        <div className={styles.mjGrid} ref={gridRef}>
          {cells.map((c) => (
            <span key={c.key} className={`${styles.mjCell} ${c.d === null ? styles.mjCellOut : ''}`}>{c.d ?? ''}</span>
          ))}
        </div>
      </div>
      <div className={styles.mjYearGrid}>
        {MONTH_LABEL.map((label, i) => (
          <button
            type="button"
            key={label}
            className={`${styles.mjYcell} ${i + 1 === current ? styles.mjYcellNow : ''}`}
            onClick={() => { human(); slideTo(i + 1); }}
          >
            {label}
          </button>
        ))}
      </div>
    </div>
  );
}