05Active-count badge pulse — a badge scaling by its change amount then settling back

<main class="stage">
  <div class="icon-btn" aria-hidden="true">
    <svg viewBox="0 0 256 256" width="28" height="28"><g fill="currentColor"><path d="M230.6 49.53A15.81 15.81 0 0 0 216 40H40a15.81 15.81 0 0 0-14.6 9.53a16 16 0 0 0 1.59 15.72L96 155.32V208a16 16 0 0 0 24.87 13.32l32-21.34a16 16 0 0 0 7.13-13.32v-31.34l68.99-90.07a16 16 0 0 0 1.61-15.72" opacity=".2"/><path d="M239.12 44.32A23.82 23.82 0 0 0 216 32H40a23.84 23.84 0 0 0-19.09 38.29L88 156.86v51.14a24 24 0 0 0 37.32 20l32-21.34A24 24 0 0 0 168 187.68v-30.82l67.09-86.57a23.84 23.84 0 0 0 4.03-25.97M152 148.79V187.7l-32 21.34v-60.25L40 40h176Z"/></g></svg>
    <span class="badge" id="badge" aria-label="Number of applied filters">1</span>
  </div>
</main>

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

$duration: $dur-quick;
$easing: $ease-pop;
$color: $subject-blue-deep;

@include stage($stage-ink);

.icon-btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 64px;
  height: 64px;
  border-radius: $r-pill;
  background: rgba($stage-paper, .1);
  color: $subject-cream;
}

.badge {
  box-sizing: border-box;
  position: absolute;
  top: -4px;
  right: -4px;
  min-width: 20px;
  height: 20px;
  padding: 0 $sp-1;
  border-radius: $r-pill;
  background: $color;
  color: $subject-cream;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 11px;
  line-height: 1;
  transform: scale(1);
  transform-origin: center;
  transition: transform $duration $easing;
}

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

@media (prefers-reduced-motion: reduce) {
  .badge { 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);
}

.icon-btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 64px;
  height: 64px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.1);
  color: #fff7e6;
}

.badge {
  box-sizing: border-box;
  position: absolute;
  top: -4px;
  right: -4px;
  min-width: 20px;
  height: 20px;
  padding: 0 4px;
  border-radius: 999px;
  background: #0a4fe8;
  color: #fff7e6;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 11px;
  line-height: 1;
  transform: scale(1);
  transform-origin: center;
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1);
}

@media (max-width: 340px) {
  .icon-btn {
    width: 52px;
    height: 52px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .badge {
    transition: none;
  }
}

// 활성 Filter 개수가 바뀌면 배지를 한 번 키웠다가(scale) 되돌린다 — transitionend 로 커진 상태가 끝났음을 확인한 뒤에만 되돌린다.
// 자동 시연만, 실사용 리스너 없음.
(function () {
  var badge = document.getElementById('badge');
  if (!badge) return;

  var VALUES = [1, 3, 2, 5, 0, 2];
  var HOLD_MS = 480;
  var idx = 0;

  function grow() {
    idx = (idx + 1) % VALUES.length;
    badge.textContent = String(VALUES[idx]);
    badge.style.transform = 'scale(1.4)';
  }

  badge.addEventListener('transitionend', function (e) {
    if (e.propertyName !== 'transform') return;
    if (badge.style.transform === 'scale(1.4)') {
      badge.style.transform = 'scale(1)';
    } else {
      setTimeout(grow, HOLD_MS);
    }
  });

  setTimeout(grow, HOLD_MS);
})();

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

// 활성 필터 개수가 바뀌면 배지를 한 번 키웠다가(scale) 되돌린다 — transitionend 로 커진 상태가 끝났음을 확인한 뒤에만 되돌린다.
// 자동 시연만, 실사용 리스너 없음.
const VALUES = [1, 3, 2, 5, 0, 2];
const HOLD_MS = 480;

export default function ActiveCountBadgePulse() {
  const badgeRef = useRef<HTMLSpanElement>(null);

  useEffect(() => {
    const badge = badgeRef.current;
    if (!badge) return;

    let alive = true;
    let idx = 0;
    let timeoutId = 0;

    function grow() {
      if (!alive) return;
      idx = (idx + 1) % VALUES.length;
      badge!.textContent = String(VALUES[idx]);
      badge!.style.transform = "scale(1.4)";
    }

    function onTransitionEnd(e: TransitionEvent) {
      if (!alive) return;
      if (e.propertyName !== "transform") return;
      if (badge!.style.transform === "scale(1.4)") {
        badge!.style.transform = "scale(1)";
      } else {
        timeoutId = window.setTimeout(grow, HOLD_MS);
      }
    }

    badge.addEventListener("transitionend", onTransitionEnd);
    timeoutId = window.setTimeout(grow, HOLD_MS);

    return () => {
      alive = false;
      badge.removeEventListener("transitionend", onTransitionEnd);
      window.clearTimeout(timeoutId);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles["icon-btn"]} aria-hidden="true">
        <svg viewBox="0 0 256 256" width="28" height="28">
          <g fill="currentColor">
            <path
              d="M230.6 49.53A15.81 15.81 0 0 0 216 40H40a15.81 15.81 0 0 0-14.6 9.53a16 16 0 0 0 1.59 15.72L96 155.32V208a16 16 0 0 0 24.87 13.32l32-21.34a16 16 0 0 0 7.13-13.32v-31.34l68.99-90.07a16 16 0 0 0 1.61-15.72"
              opacity=".2"
            />
            <path d="M239.12 44.32A23.82 23.82 0 0 0 216 32H40a23.84 23.84 0 0 0-19.09 38.29L88 156.86v51.14a24 24 0 0 0 37.32 20l32-21.34A24 24 0 0 0 168 187.68v-30.82l67.09-86.57a23.84 23.84 0 0 0 4.03-25.97M152 148.79V187.7l-32 21.34v-60.25L40 40h176Z" />
          </g>
        </svg>
        <span ref={badgeRef} className={styles.badge} aria-label="적용된 필터 개수">
          1
        </span>
      </div>
    </main>
  );
}