02Expiry-separator value toggle — once the month and year digit values fill in, a separator value automatically appears between them

<main class="stage">
<div class="ce is-demo" id="ce">
  <label class="ce__field">
    <input class="ce__input" id="ceInput" type="text" inputmode="numeric" autocomplete="off" spellcheck="false" maxlength="5" value="" placeholder="MM/YY">
  </label>
  <div class="ce__chips" id="ceChips" aria-hidden="true">
    <span class="ce__chip" id="ceMm">MM</span>
    <span class="ce__slash" id="ceSlash">/</span>
    <span class="ce__chip" id="ceYy">YY</span>
  </div>
</div>
</main>

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

// 계산 겹: 월 값을 01~12 로 clamp 하고, 완료 시 구분자 값을 자동 삽입한다(index.html).
@include stage($stage-yellow);

.ce {
  width: 100%;
  max-width: 280px;
  display: grid;
  gap: $sp-4;
  justify-items: center;
}

.ce__field { display: block; width: 100%; }

.ce__input {
  width: 100%;
  box-sizing: border-box;
  padding: $sp-3 $sp-4;
  border-radius: $r-control;
  border: 0;
  background: $subject-ink;
  color: $subject-cream;
  font-weight: 600;
  font-size: 18px;
  line-height: 1.3;
  font-family: "SFMono-Regular", Consolas, monospace;
  letter-spacing: .08em;
  text-align: center;

  &::placeholder { color: rgba($subject-cream, .5); }
  &:focus { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }
}

.ce__chips {
  display: flex;
  align-items: center;
  gap: $sp-2;
}

.ce__chip {
  min-width: 56px;
  box-sizing: border-box;
  padding: $sp-2 $sp-3;
  border-radius: $r-sm;
  background: $subject-cream;
  color: rgba($subject-ink, .4);
  font-weight: 700;
  font-size: 15px;
  text-align: center;
  transition: color $dur-quick $ease-out;
}

.ce__chip--on { color: $subject-ink; }

.ce__chip--pulse { animation: cePulse $dur-enter $ease-elastic; }

.ce__slash {
  font-weight: 700;
  font-size: 18px;
  color: rgba($subject-ink, .35);
  transform: scale(.4);
  opacity: 0;
  transition: transform $dur-quick $ease-elastic, opacity $dur-quick $ease-out;
}

.ce__slash--on {
  transform: scale(1);
  opacity: 1;
  color: $subject-ink;
}

@keyframes cePulse {
  0% { transform: scale(1); }
  30% { transform: scale(1.16); }
  60% { transform: scale(.96); }
  100% { transform: scale(1); }
}

@media (max-width: 340px) {
  .ce { max-width: 240px; }
  .ce__input { padding: $sp-2 $sp-3; font-size: 16px; }
  .ce__chip { min-width: 48px; font-size: 13px; }
}

@media (prefers-reduced-motion: reduce) {
  .ce__slash { transition: none; }
  .ce__chip--pulse { animation: none; }
  .ce__chip { 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);
}

.ce {
  width: 100%;
  max-width: 280px;
  display: grid;
  gap: 16px;
  justify-items: center;
}

.ce__field {
  display: block;
  width: 100%;
}

.ce__input {
  width: 100%;
  box-sizing: border-box;
  padding: 12px 16px;
  border-radius: 12px;
  border: 0;
  background: #17141a;
  color: #fff7e6;
  font-weight: 600;
  font-size: 18px;
  line-height: 1.3;
  font-family: "SFMono-Regular", Consolas, monospace;
  letter-spacing: 0.08em;
  text-align: center;
}
.ce__input::placeholder {
  color: rgba(255, 247, 230, 0.5);
}
.ce__input:focus {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.ce__chips {
  display: flex;
  align-items: center;
  gap: 8px;
}

.ce__chip {
  min-width: 56px;
  box-sizing: border-box;
  padding: 8px 12px;
  border-radius: 8px;
  background: #fff7e6;
  color: rgba(23, 20, 26, 0.4);
  font-weight: 700;
  font-size: 15px;
  text-align: center;
  transition: color 220ms ease-out;
}

.ce__chip--on {
  color: #17141a;
}

.ce__chip--pulse {
  animation: cePulse 600ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

.ce__slash {
  font-weight: 700;
  font-size: 18px;
  color: rgba(23, 20, 26, 0.35);
  transform: scale(0.4);
  opacity: 0;
  transition: transform 220ms cubic-bezier(0.34, 1.56, 0.64, 1), opacity 220ms ease-out;
}

.ce__slash--on {
  transform: scale(1);
  opacity: 1;
  color: #17141a;
}

@keyframes cePulse {
  0% {
    transform: scale(1);
  }
  30% {
    transform: scale(1.16);
  }
  60% {
    transform: scale(0.96);
  }
  100% {
    transform: scale(1);
  }
}
@media (max-width: 340px) {
  .ce {
    max-width: 240px;
  }
  .ce__input {
    padding: 8px 12px;
    font-size: 16px;
  }
  .ce__chip {
    min-width: 48px;
    font-size: 13px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ce__slash {
    transition: none;
  }
  .ce__chip--pulse {
    animation: none;
  }
  .ce__chip {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('ce');
  var input = document.getElementById('ceInput');
  var mmChip = document.getElementById('ceMm');
  var yyChip = document.getElementById('ceYy');
  var slash = document.getElementById('ceSlash');

  // 계산 겹: 월 값의 범위를 01~12 로 clamp 하고, 월 자릿수 값이 2자리를 채우면
  // 구분자(슬래시) 값을 자동으로 끼운다.
  function digitsOnly(str) { return str.replace(/\D/g, '').slice(0, 4); }

  function build(rawDigits) {
    var mm = rawDigits.slice(0, 2);
    var yy = rawDigits.slice(2, 4);
    var clamped = false;
    if (mm.length === 2) {
      var n = parseInt(mm, 10);
      if (n === 0) { mm = '01'; clamped = true; }
      else if (n > 12) { mm = '12'; clamped = true; }
    }
    var slashOn = mm.length === 2;
    return { display: mm + (slashOn ? '/' : '') + yy, mm: mm, yy: yy, slashOn: slashOn, clamped: clamped };
  }

  function pulse(el) {
    el.classList.remove('ce__chip--pulse');
    void el.offsetWidth;
    el.classList.add('ce__chip--pulse');
  }

  function paint(r) {
    mmChip.textContent = r.mm || 'MM';
    mmChip.classList.toggle('ce__chip--on', r.mm.length > 0);
    yyChip.textContent = r.yy || 'YY';
    yyChip.classList.toggle('ce__chip--on', r.yy.length > 0);
    slash.classList.toggle('ce__slash--on', r.slashOn);
    if (r.clamped) pulse(mmChip);
  }

  function digitsBefore(str, upto) { return str.slice(0, upto).replace(/\D/g, '').length; }

  input.addEventListener('input', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    var prevDigits = digitsBefore(input.value, input.selectionStart);
    var rawDigits = digitsOnly(input.value);
    var r = build(rawDigits);
    input.value = r.display;
    var newCaret = Math.min(prevDigits + (r.slashOn && prevDigits >= 2 ? 1 : 0), input.value.length);
    input.setSelectionRange(newCaret, newCaret);
    paint(r);
  });

  // 자동 루프: 시드 고정 자릿수 값 — "13" 을 쳐서 월 범위 clamp("12")가 걸리는 장면 포함.
  var SEQ = ['', '1', '13', '132', '1329', '132', '13', '1', ''];
  var si = 0;
  var autoTimer = null;
  function autoTick() {
    var rawDigits = SEQ[si];
    var r = build(rawDigits);
    input.value = r.display;
    paint(r);
    si = (si + 1) % SEQ.length;
  }
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (!reduce) { autoTimer = setInterval(autoTick, 340); autoTick(); }
  else { autoTick(); }
})();

import { useEffect, useRef } from "react";
import styles from "./ExpiryAutoSlash.module.scss";

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

type Built = { display: string; mm: string; yy: string; slashOn: boolean; clamped: boolean };

export default function ExpiryAutoSlash() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement | null>;

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const input = root.querySelector(`.${styles.input}`) as HTMLInputElement | null;
    const mmChip = root.querySelector(`.${styles.mm}`) as HTMLElement | null;
    const yyChip = root.querySelector(`.${styles.yy}`) as HTMLElement | null;
    const slash = root.querySelector(`.${styles.slash}`) as HTMLElement | null;
    if (!input || !mmChip || !yyChip || !slash) return;

    // 계산 겹: 월 값의 범위를 01~12 로 clamp 하고, 월 자릿수 값이 2자리를 채우면
    // 구분자(슬래시) 값을 자동으로 끼운다.
    function digitsOnly(str: string) { return str.replace(/\D/g, "").slice(0, 4); }

    function build(rawDigits: string): Built {
      let mm = rawDigits.slice(0, 2);
      const yy = rawDigits.slice(2, 4);
      let clamped = false;
      if (mm.length === 2) {
        const n = parseInt(mm, 10);
        if (n === 0) { mm = "01"; clamped = true; }
        else if (n > 12) { mm = "12"; clamped = true; }
      }
      const slashOn = mm.length === 2;
      return { display: mm + (slashOn ? "/" : "") + yy, mm, yy, slashOn, clamped };
    }

    function pulse(el: HTMLElement) {
      el.classList.remove(styles["chip--pulse"]);
      void el.offsetWidth;
      el.classList.add(styles["chip--pulse"]);
    }

    function paint(r: Built) {
      mmChip!.textContent = r.mm || "MM";
      mmChip!.classList.toggle(styles["chip--on"], r.mm.length > 0);
      yyChip!.textContent = r.yy || "YY";
      yyChip!.classList.toggle(styles["chip--on"], r.yy.length > 0);
      slash!.classList.toggle(styles["slash--on"], r.slashOn);
      if (r.clamped) pulse(mmChip!);
    }

    function digitsBefore(str: string, upto: number) {
      return str.slice(0, upto).replace(/\D/g, "").length;
    }

    function onInput() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      const prevDigits = digitsBefore(input!.value, input!.selectionStart || 0);
      const rawDigits = digitsOnly(input!.value);
      const r = build(rawDigits);
      input!.value = r.display;
      const newCaret = Math.min(prevDigits + (r.slashOn && prevDigits >= 2 ? 1 : 0), input!.value.length);
      input!.setSelectionRange(newCaret, newCaret);
      paint(r);
    }
    input.addEventListener("input", onInput);

    // 자동 루프: 시드 고정 자릿수 값 — "13" 을 쳐서 월 범위 clamp("12")가 걸리는 장면 포함.
    const SEQ = ["", "1", "13", "132", "1329", "132", "13", "1", ""];
    let si = 0;
    let autoTimer: number | null = null;
    function autoTick() {
      const rawDigits = SEQ[si];
      const r = build(rawDigits);
      input!.value = r.display;
      paint(r);
      si = (si + 1) % SEQ.length;
    }
    function stopAutoplay() {
      if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; }
    }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoTimer = window.setInterval(autoTick, 340); autoTick(); }
    else { autoTick(); }

    return () => {
      stopAutoplay();
      input.removeEventListener("input", onInput);
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.ce} ${styles["is-demo"]}`}>
      <label className={styles.field}>
        <input className={styles.input} type="text" inputMode="numeric" autoComplete="off" spellCheck={false} maxLength={5} defaultValue="" placeholder="MM/YY" />
      </label>
      <div className={styles.chips} aria-hidden="true">
        <span className={`${styles.chip} ${styles.mm}`}>MM</span>
        <span className={styles.slash}>/</span>
        <span className={`${styles.chip} ${styles.yy}`}>YY</span>
      </div>
    </div>
  );
}