02Hiệu ứng gõ chữ bằng steps()

<main class="stage">
  <p class="type"><span class="type__text">Copy dán một dòng là xong</span></p>
</main>

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

$duration: $dur-loop;                      // 한 루프 전체 길이
$easing: steps(10, end);                   // 글자 수만큼 뚝뚝 끊어 늘어나는 곡선
$color: $subject-ink;                      // 글자·커서 색

@include stage($stage-yellow);

.type {
  margin: 0;

  &__text {
    display: inline-block;
    overflow: hidden;
    white-space: nowrap;
    width: 0;
    border-right: .12em solid $color;
    font-weight: 700; font-size: clamp(20px, 5.6vw, 34px); line-height: 1.4; font-family: inherit;
    color: $color;
    animation: type-loop $duration linear infinite;
  }
}

@keyframes type-loop {
  0%, 6%  { width: 0; animation-timing-function: $easing; }
  58%     { width: var(--full, 10ch); }
  88%     { width: var(--full, 10ch); }
  94%, 100% { width: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .type__text { animation: none; width: var(--full, 10ch); border-right-color: transparent; }
}

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);
}

.type {
  margin: 0;
}
.type__text {
  display: inline-block;
  overflow: hidden;
  white-space: nowrap;
  width: 0;
  border-right: 0.12em solid #17141a;
  font-weight: 700;
  font-size: clamp(20px, 5.6vw, 34px);
  line-height: 1.4;
  font-family: inherit;
  color: #17141a;
  animation: type-loop 2s linear infinite;
}

@keyframes type-loop {
  0%, 6% {
    width: 0;
    animation-timing-function: steps(10, end);
  }
  58% {
    width: var(--full, 10ch);
  }
  88% {
    width: var(--full, 10ch);
  }
  94%, 100% {
    width: 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .type__text {
    animation: none;
    width: var(--full, 10ch);
    border-right-color: transparent;
  }
}

(function () {
  var el = document.querySelector('.type__text'), cv = document.createElement('canvas').getContext('2d');
  cv.font = getComputedStyle(el).font;
  el.style.setProperty('--full', Math.ceil(cv.measureText(el.textContent).width) + 'px');
})();

import { useEffect, useRef } from "react";
import type { CSSProperties } from "react";
import styles from "./StepsTypewriter.module.scss";

export type StepsTypewriterProps = {
  text: string;
  /** 한 루프 전체 길이 (기본 2000ms) */
  duration?: number;
  color?: string;
};

export default function StepsTypewriter({ text, duration = 2000, color = "#17141a" }: StepsTypewriterProps) {
  const ref = useRef<HTMLSpanElement | null>(null);
  useEffect(() => {
    const el = ref.current;
    const cv = el && document.createElement("canvas").getContext("2d");
    if (!el || !cv) return;
    cv.font = getComputedStyle(el).font;
    el.style.setProperty("--full", Math.ceil(cv.measureText(text).width) + "px");
  }, [text]);
  const vars = { "--duration": `${duration}ms`, "--color": color, "--easing": `steps(${text.length}, end)` } as CSSProperties;
  return (
    <p className={styles.type} style={vars}>
      <span ref={ref} className={styles.text}>{text}</span>
    </p>
  );
}