05Split-dual value reveal — when a confirm value turns on, the button splits into two pieces, each revealing a different value

<main class="stage">
<div class="sd is-demo" id="sd">
  <div class="sd__shell" id="sdShell">
    <div class="sd__half sd__half--l" aria-hidden="true"></div>
    <div class="sd__half sd__half--r" aria-hidden="true"></div>
    <div class="sd__face sd__face--rest" id="sdRest">
      <span class="sd__label">Delete item value</span>
    </div>
    <div class="sd__face sd__face--split" id="sdSplit">
      <button type="button" class="sd__choice" id="sdNo">Cancel</button>
      <button type="button" class="sd__choice sd__choice--danger" id="sdYes">Erase</button>
    </div>
  </div>
</div>
</main>

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

// 계산 겹: 두 절반이 PART_PX(26px) 만큼 각자 바깥으로 벌어지고(translateX ±), 그 사이로
// 안의 선택 값 두 개가 크로스페이드로 뒤바뀐다(index.html). 절반 폭은 셸 폭 50% 실측.
@include stage($stage-ink);

.sd {
  display: grid;
  justify-items: center;
}

.sd__shell {
  position: relative;
  width: 240px;
  height: 56px;
  cursor: pointer;
}

.sd__half {
  position: absolute;
  top: 0;
  width: calc(var(--shell-w, 240px) / 2);
  height: 100%;
  border-radius: $r-pill;
  background: $error-soft;
  transition: transform $dur-enter $ease-elastic, background-color $dur-quick $ease-out;

  &--l { left: 0; border-top-right-radius: 0; border-bottom-right-radius: 0; }
  &--r { right: 0; border-top-left-radius: 0; border-bottom-left-radius: 0; }
}

.sd__face {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: $sp-3;
}

.sd__face--rest {
  transition: opacity $dur-quick $ease-out;
}

.sd__label {
  color: $error;
  font-weight: 700;
  font-size: 16px;
}

.sd__face--split {
  opacity: 0;
  transition: opacity $dur-quick $ease-out;
}

.sd__choice {
  border: 0;
  border-radius: $r-pill;
  background: $stage-paper;
  color: $subject-ink;
  font-weight: 600;
  font-size: 13px;
  padding: $sp-2 $sp-4;
  cursor: pointer;

  &--danger { background: $error; color: $subject-cream; }
}

.sd--split {
  .sd__half--l { transform: translateX(-26px); background: $error-soft; }
  .sd__half--r { transform: translateX(26px); }
  .sd__face--rest { opacity: 0; }
  .sd__face--split { opacity: 1; }
}

@media (max-width: 340px) {
  .sd__shell { width: 210px; height: 52px; }
}

@media (prefers-reduced-motion: reduce) {
  .sd__half, .sd__face--rest, .sd__face--split { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sd {
  display: grid;
  justify-items: center;
}

.sd__shell {
  position: relative;
  width: 240px;
  height: 56px;
  cursor: pointer;
}

.sd__half {
  position: absolute;
  top: 0;
  width: calc(var(--shell-w, 240px) / 2);
  height: 100%;
  border-radius: 999px;
  background: #ffe0d8;
  transition: transform 600ms cubic-bezier(0.34, 1.56, 0.64, 1), background-color 220ms ease-out;
}
.sd__half--l {
  left: 0;
  border-top-right-radius: 0;
  border-bottom-right-radius: 0;
}
.sd__half--r {
  right: 0;
  border-top-left-radius: 0;
  border-bottom-left-radius: 0;
}

.sd__face {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
}

.sd__face--rest {
  transition: opacity 220ms ease-out;
}

.sd__label {
  color: #c2361a;
  font-weight: 700;
  font-size: 16px;
}

.sd__face--split {
  opacity: 0;
  transition: opacity 220ms ease-out;
}

.sd__choice {
  border: 0;
  border-radius: 999px;
  background: #ffffff;
  color: #17141a;
  font-weight: 600;
  font-size: 13px;
  padding: 8px 16px;
  cursor: pointer;
}
.sd__choice--danger {
  background: #c2361a;
  color: #fff7e6;
}

.sd--split .sd__half--l {
  transform: translateX(-26px);
  background: #ffe0d8;
}
.sd--split .sd__half--r {
  transform: translateX(26px);
}
.sd--split .sd__face--rest {
  opacity: 0;
}
.sd--split .sd__face--split {
  opacity: 1;
}

@media (max-width: 340px) {
  .sd__shell {
    width: 210px;
    height: 52px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .sd__half, .sd__face--rest, .sd__face--split {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('sd');
  var shell = document.getElementById('sdShell');
  var PART_PX = 26; // 계산 겹: 두 절반이 벌어지는 거리(px) — 셸 폭 절반 기준 산술

  // 계산 겹: 셸 폭을 getBoundingClientRect 로 실측해 --shell-w 로 넘긴다.
  // 절반은 각자 셸 폭의 50% 로 그려지므로 벌어짐 거리도 이 값에 맞춘다.
  function measure() {
    shell.style.setProperty('--shell-w', shell.getBoundingClientRect().width + 'px');
  }

  var split = false;
  function paint() {
    root.classList.toggle('sd--split', split);
    shell.setAttribute('aria-expanded', String(split));
  }

  function toggle() {
    split = !split;
    paint();
  }

  shell.addEventListener('click', function (e) {
    if (e.target.closest('.sd__choice')) return;
    root.classList.remove('is-demo');
    stopAutoplay();
    if (!split) toggle();
  });
  document.getElementById('sdNo').addEventListener('click', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    if (split) toggle();
  });
  document.getElementById('sdYes').addEventListener('click', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    if (split) toggle();
  });

  var autoTimer = null;
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  measure();
  if (!reduce) { autoTimer = setInterval(toggle, 1400); }
  else { split = true; paint(); }
})();

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

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

const PART_PX = 26; // 계산 겹: 두 절반이 벌어지는 거리(px) — 셸 폭 절반 기준 산술

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

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const shell = root.querySelector(`.${styles.shell}`) as HTMLElement | null;
    if (!shell) return;

    function measure() {
      shell!.style.setProperty("--shell-w", shell!.getBoundingClientRect().width + "px");
    }

    let split = false;
    function paint() {
      root!.classList.toggle(styles["root--split"], split);
      shell!.setAttribute("aria-expanded", String(split));
    }
    function toggle() {
      split = !split;
      paint();
    }

    function onShellClick(e: Event) {
      const t = e.target as HTMLElement;
      if (t.closest("." + styles.choice)) return;
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      if (!split) toggle();
    }
    function onChoice() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      if (split) toggle();
    }
    shell.addEventListener("click", onShellClick);
    root.querySelectorAll("." + styles.choice).forEach((b) => {
      b.addEventListener("click", onChoice);
    });

    let autoTimer: number | null = null;
    function stopAutoplay() { if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; } }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    measure();
    if (!reduce) { autoTimer = window.setInterval(toggle, 1400); }
    else { split = true; paint(); }

    return () => {
      stopAutoplay();
      shell.removeEventListener("click", onShellClick);
      root.querySelectorAll("." + styles.choice).forEach((b) => {
        b.removeEventListener("click", onChoice);
      });
    };
  }, []);

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.sd} ${styles["is-demo"]}`}>
      <div className={styles.shell} aria-expanded="false">
        <div className={`${styles.half} ${styles["half--l"]}`} aria-hidden="true" />
        <div className={`${styles.half} ${styles["half--r"]}`} aria-hidden="true" />
        <div className={`${styles.face} ${styles["face--rest"]}`}>
          <span className={styles.label}>항목 값 삭제</span>
        </div>
        <div className={`${styles.face} ${styles["face--split"]}`}>
          <button type="button" className={styles.choice}>그만두기</button>
          <button type="button" className={`${styles.choice} ${styles["choice--danger"]}`}>지우기</button>
        </div>
      </div>
    </div>
  );
}