01Digit-group value toggle — as the entered digit value reaches every fourth position, a spacing value automatically appears between groups

<main class="stage">
<div class="ci is-demo" id="ci">
  <label class="ci__field">
    <input class="ci__input" id="ciInput" type="text" inputmode="numeric" autocomplete="off" spellcheck="false" maxlength="19" value="">
  </label>
  <div class="ci__track" id="ciTrack" aria-hidden="true">
    <span class="ci__seg" data-g="0"><span class="ci__segFill"></span></span>
    <span class="ci__gap" data-gap="0"></span>
    <span class="ci__seg" data-g="1"><span class="ci__segFill"></span></span>
    <span class="ci__gap" data-gap="1"></span>
    <span class="ci__seg" data-g="2"><span class="ci__segFill"></span></span>
    <span class="ci__gap" data-gap="2"></span>
    <span class="ci__seg" data-g="3"><span class="ci__segFill"></span></span>
  </div>
</div>
</main>

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

// 계산 겹: 커서 위치 값을 digit count 로 환산해 간격 값 삽입 개수만큼 보정한다(index.html).
@include stage($stage-ink);

.ci {
  width: 100%;
  max-width: 320px;
  display: grid;
  gap: $sp-4;
}

.ci__field { display: block; }

.ci__input {
  width: 100%;
  box-sizing: border-box;
  padding: $sp-3 $sp-4;
  border-radius: $r-control;
  border: 0;
  background: $subject-cream;
  color: $subject-ink;
  font-weight: 600;
  font-size: 18px;
  line-height: 1.3;
  font-family: "SFMono-Regular", Consolas, monospace;
  letter-spacing: .06em;

  &:focus { outline: 2px solid $subject-blue-light; outline-offset: 2px; }
}

.ci__track {
  display: flex;
  align-items: center;
  gap: $sp-1;
}

.ci__seg {
  flex: 1;
  height: $sp-1;
  border-radius: $r-xs;
  background: rgba($subject-cream, .16);
  overflow: hidden;
}

.ci__segFill {
  display: block;
  width: 100%;
  height: 100%;
  border-radius: $r-xs;
  background: $subject-blue-light;
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform $dur-quick $ease-out;
}

.ci__gap {
  width: $sp-1;
  height: $sp-1;
  border-radius: 50%;
  background: rgba($subject-cream, .16);
  transform: scale(.4);
  opacity: 0;
  transition: transform $dur-quick $ease-elastic, opacity $dur-quick $ease-out, background-color $dur-quick $ease-out;
}

.ci__gap--on {
  opacity: 1;
  transform: scale(1);
  background: $subject-blue-light;
}

@media (max-width: 340px) {
  .ci__input { padding: $sp-2 $sp-3; font-size: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  .ci__segFill, .ci__gap { 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);
}

.ci {
  width: 100%;
  max-width: 320px;
  display: grid;
  gap: 16px;
}

.ci__field {
  display: block;
}

.ci__input {
  width: 100%;
  box-sizing: border-box;
  padding: 12px 16px;
  border-radius: 12px;
  border: 0;
  background: #fff7e6;
  color: #17141a;
  font-weight: 600;
  font-size: 18px;
  line-height: 1.3;
  font-family: "SFMono-Regular", Consolas, monospace;
  letter-spacing: 0.06em;
}
.ci__input:focus {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.ci__track {
  display: flex;
  align-items: center;
  gap: 4px;
}

.ci__seg {
  flex: 1;
  height: 4px;
  border-radius: 4px;
  background: rgba(255, 247, 230, 0.16);
  overflow: hidden;
}

.ci__segFill {
  display: block;
  width: 100%;
  height: 100%;
  border-radius: 4px;
  background: #5b8cf8;
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 220ms ease-out;
}

.ci__gap {
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: rgba(255, 247, 230, 0.16);
  transform: scale(0.4);
  opacity: 0;
  transition: transform 220ms cubic-bezier(0.34, 1.56, 0.64, 1), opacity 220ms ease-out, background-color 220ms ease-out;
}

.ci__gap--on {
  opacity: 1;
  transform: scale(1);
  background: #5b8cf8;
}

@media (max-width: 340px) {
  .ci__input {
    padding: 8px 12px;
    font-size: 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ci__segFill, .ci__gap {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('ci');
  var input = document.getElementById('ciInput');
  var track = document.getElementById('ciTrack');
  var segFills = track.querySelectorAll('.ci__segFill');
  var gaps = track.querySelectorAll('.ci__gap');

  // 계산 겹: 자릿수 값을 4개씩 묶어 다시 조립하고, 커서 위치 값을 digit count 로
  // 환산해 삽입된 간격 값 개수만큼 보정한다 — 그냥 재대입하면 커서가 맨 끝으로 튄다.
  function digitsBefore(str, upto) { return str.slice(0, upto).replace(/\D/g, '').length; }

  function groupsOf(rawDigits) {
    var g = rawDigits.match(/.{1,4}/g) || [];
    while (g.length < 4) g.push('');
    return g;
  }

  function paintTrack(rawDigits) {
    var g = groupsOf(rawDigits);
    for (var i = 0; i < 4; i++) {
      segFills[i].style.transform = 'scaleX(' + (g[i].length / 4) + ')';
    }
    for (var j = 0; j < 3; j++) {
      var on = rawDigits.length > (j + 1) * 4;
      gaps[j].classList.toggle('ci__gap--on', on);
    }
  }

  function reformat(prevCaret) {
    var prevDigits = digitsBefore(input.value, prevCaret);
    var rawDigits = input.value.replace(/\D/g, '').slice(0, 16);
    var groups = rawDigits.match(/.{1,4}/g) || [];
    input.value = groups.join(' ');
    // 커서 위치 보정: 앞선 자릿수 값 개수 + 그 앞에 이미 생긴 간격 값 개수(4자리마다 1개)
    var spacesBefore = Math.floor(Math.max(prevDigits - 1, 0) / 4);
    var newCaret = Math.min(prevDigits + spacesBefore, input.value.length);
    input.setSelectionRange(newCaret, newCaret);
    paintTrack(rawDigits);
  }

  input.addEventListener('input', function () {
    root.classList.remove('is-demo');
    stopAutoplay();
    reformat(input.selectionStart);
  });

  // 자동 루프: 시드 고정 자릿수 값을 한 자리씩 늘렸다 줄인다.
  var FULL = '9999999999999995';
  var SEQ = [];
  for (var i = 0; i <= FULL.length; i++) SEQ.push(FULL.slice(0, i));
  for (var k = FULL.length - 1; k >= 0; k--) SEQ.push(FULL.slice(0, k));
  var si = 0;
  var autoTimer = null;
  function autoTick() {
    var rawDigits = SEQ[si];
    var groups = rawDigits.match(/.{1,4}/g) || [];
    input.value = groups.join(' ');
    paintTrack(rawDigits);
    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, 160); autoTick(); }
  else { autoTick(); }
})();

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

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

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

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const input = root.querySelector(`.${styles.input}`) as HTMLInputElement | null;
    const segFills = root.querySelectorAll(`.${styles.segFill}`);
    const gaps = root.querySelectorAll(`.${styles.gap}`);
    if (!input || segFills.length === 0) return;

    // 계산 겹: 자릿수 값을 4개씩 묶어 다시 조립하고, 커서 위치 값을 digit count 로
    // 환산해 삽입된 간격 값 개수만큼 보정한다 — 그냥 재대입하면 커서가 맨 끝으로 튄다.
    function digitsBefore(str: string, upto: number) {
      return str.slice(0, upto).replace(/\D/g, "").length;
    }

    function groupsOf(rawDigits: string) {
      const g: string[] = rawDigits.match(/.{1,4}/g) || [];
      while (g.length < 4) g.push("");
      return g;
    }

    function paintTrack(rawDigits: string) {
      const g = groupsOf(rawDigits);
      for (let i = 0; i < 4; i++) {
        (segFills[i] as HTMLElement).style.transform = "scaleX(" + g[i].length / 4 + ")";
      }
      for (let j = 0; j < 3; j++) {
        const on = rawDigits.length > (j + 1) * 4;
        gaps[j].classList.toggle(styles["gap--on"], on);
      }
    }

    function reformat(prevCaret: number) {
      const prevDigits = digitsBefore(input!.value, prevCaret);
      const rawDigits = input!.value.replace(/\D/g, "").slice(0, 16);
      const groups = rawDigits.match(/.{1,4}/g) || [];
      input!.value = groups.join(" ");
      // 커서 위치 보정: 앞선 자릿수 값 개수 + 그 앞에 이미 생긴 간격 값 개수(4자리마다 1개)
      const spacesBefore = Math.floor(Math.max(prevDigits - 1, 0) / 4);
      const newCaret = Math.min(prevDigits + spacesBefore, input!.value.length);
      input!.setSelectionRange(newCaret, newCaret);
      paintTrack(rawDigits);
    }

    function onInput() {
      root!.classList.remove(styles["is-demo"]);
      stopAutoplay();
      reformat(input!.selectionStart || 0);
    }
    input.addEventListener("input", onInput);

    // 자동 루프: 시드 고정 자릿수 값을 한 자리씩 늘렸다 줄인다.
    const FULL = "9999999999999995";
    const SEQ: string[] = [];
    for (let i = 0; i <= FULL.length; i++) SEQ.push(FULL.slice(0, i));
    for (let k = FULL.length - 1; k >= 0; k--) SEQ.push(FULL.slice(0, k));
    let si = 0;
    let autoTimer: number | null = null;
    function autoTick() {
      const rawDigits = SEQ[si];
      const groups = rawDigits.match(/.{1,4}/g) || [];
      input!.value = groups.join(" ");
      paintTrack(rawDigits);
      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, 160); autoTick(); }
    else { autoTick(); }

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

  return (
    <div ref={rootRef} className={`${styles.stage} ${styles.ci} ${styles["is-demo"]}`}>
      <label className={styles.field}>
        <input className={styles.input} type="text" inputMode="numeric" autoComplete="off" spellCheck={false} maxLength={19} defaultValue="" />
      </label>
      <div className={styles.track} aria-hidden="true">
        <span className={styles.seg}><span className={styles.segFill} /></span>
        <span className={styles.gap} />
        <span className={styles.seg}><span className={styles.segFill} /></span>
        <span className={styles.gap} />
        <span className={styles.seg}><span className={styles.segFill} /></span>
        <span className={styles.gap} />
        <span className={styles.seg}><span className={styles.segFill} /></span>
      </div>
    </div>
  );
}