08Loading ngay trong nút

<main class="stage">
  <button class="btn is-demo" type="button">
    <span class="btn__label">Lưu</span>
    <span class="btn__spin" aria-hidden="true"></span>
  </button>
</main>

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

$duration: $dur-quick;                            // 글자 ↔ 스피너 교체
$spin: .8s;                                       // 스피너 한 바퀴
$color: $subject-blue;                            // 버튼 색

@include stage($stage-paper);

.btn {
  position: relative;
  display: grid;
  place-items: center;
  min-width: clamp(150px, 40vw, 200px);            // 폭을 고정해 글자가 사라져도 안 줄어든다
  border: 0;
  border-radius: $r-control;
  padding: clamp(14px, 4vw, 22px) clamp(24px, 6vw, 40px);
  font-weight: 700;
  font-size: clamp(15px, 4vw, 20px);
  line-height: 1;
  font-family: inherit;
  color: $subject-cream;
  background: $color;
  cursor: pointer;

  &__label, &__spin { grid-area: 1 / 1; transition: opacity $duration, transform $duration; }
  &__spin {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    border: 3px solid rgba($subject-cream, .35);
    border-top-color: $subject-cream;
    opacity: 0;
    transform: scale(.6);
    animation: spin $spin linear infinite;
  }
  &.is-loading &__label { opacity: 0; transform: translateY(6px); }
  &.is-loading &__spin  { opacity: 1; transform: scale(1); }

  // 데모: 2초 주기로 스스로 눌린 것처럼 반복한다
  &.is-demo &__label { animation: label-loop $dur-loop ease infinite; }
  &.is-demo &__spin  { animation: spin $spin linear infinite, spin-loop $dur-loop ease infinite; }
}

@keyframes spin { to { transform: rotate(360deg); } }
@keyframes label-loop {
  0%, 30%  { opacity: 1; transform: none; }
  45%, 80% { opacity: 0; transform: translateY(6px); }
  95%, 100% { opacity: 1; transform: none; }
}
@keyframes spin-loop {
  0%, 30%  { opacity: 0; }
  45%, 80% { opacity: 1; }
  95%, 100% { opacity: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .btn__label, .btn__spin { transition: none; animation: none !important; }
  .btn.is-loading .btn__spin { opacity: 1; transform: none; border-top-color: rgba($subject-cream, .35); }
}

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

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

.btn {
  position: relative;
  display: grid;
  place-items: center;
  min-width: clamp(150px, 40vw, 200px);
  border: 0;
  border-radius: 12px;
  padding: clamp(14px, 4vw, 22px) clamp(24px, 6vw, 40px);
  font-weight: 700;
  font-size: clamp(15px, 4vw, 20px);
  line-height: 1;
  font-family: inherit;
  color: #fff7e6;
  background: #2f6df6;
  cursor: pointer;
}
.btn__label, .btn__spin {
  grid-area: 1/1;
  transition: opacity 220ms, transform 220ms;
}
.btn__spin {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 3px solid rgba(255, 247, 230, 0.35);
  border-top-color: #fff7e6;
  opacity: 0;
  transform: scale(0.6);
  animation: spin 0.8s linear infinite;
}
.btn.is-loading .btn__label {
  opacity: 0;
  transform: translateY(6px);
}
.btn.is-loading .btn__spin {
  opacity: 1;
  transform: scale(1);
}
.btn.is-demo .btn__label {
  animation: label-loop 2s ease infinite;
}
.btn.is-demo .btn__spin {
  animation: spin 0.8s linear infinite, spin-loop 2s ease infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}
@keyframes label-loop {
  0%, 30% {
    opacity: 1;
    transform: none;
  }
  45%, 80% {
    opacity: 0;
    transform: translateY(6px);
  }
  95%, 100% {
    opacity: 1;
    transform: none;
  }
}
@keyframes spin-loop {
  0%, 30% {
    opacity: 0;
  }
  45%, 80% {
    opacity: 1;
  }
  95%, 100% {
    opacity: 0;
  }
}
@media (prefers-reduced-motion: reduce) {
  .btn__label, .btn__spin {
    transition: none;
    animation: none !important;
  }
  .btn.is-loading .btn__spin {
    opacity: 1;
    transform: none;
    border-top-color: rgba(255, 247, 230, 0.35);
  }
}

// 실제로는 fetch 시작 시 is-loading 을 붙이고 응답이 오면 뗀다. 데모는 2초 주기로 스스로 반복한다.
var b = document.querySelector('.btn');
b.addEventListener('pointerdown', function () {
  b.classList.remove('is-demo');
  b.classList.add('is-loading');
  b.disabled = true;
  setTimeout(function () {
    b.classList.remove('is-loading');
    b.disabled = false;
  }, 900);
});

import { useCallback, useState } from "react";
import type { CSSProperties, MouseEvent, ReactNode } from "react";
import styles from "./InlineSpinnerButton.module.scss";

export type InlineSpinnerButtonProps = {
  children: ReactNode;
  /** 글자 ↔ 스피너 교체 시간 (기본 220ms) */
  duration?: number;
  /** 스피너 한 바퀴 시간 (기본 800ms) */
  spin?: number;
  /** 버튼 색 */
  color?: string;
  /** 로딩을 유지할 시간 (기본 900ms, 실제로는 fetch 응답 시점) */
  loadingMs?: number;
  onClick?: (e: MouseEvent<HTMLButtonElement>) => void;
  type?: "button" | "submit";
};

type Vars = CSSProperties & { "--duration"?: string; "--spin"?: string; "--color"?: string };

export default function InlineSpinnerButton({
  children,
  duration = 220,
  spin = 800,
  color = "#2f6df6",
  loadingMs = 900,
  onClick,
  type = "button",
}: InlineSpinnerButtonProps) {
  const [loading, setLoading] = useState(false);

  const handle = useCallback(
    (e: MouseEvent<HTMLButtonElement>) => {
      setLoading(true);
      onClick?.(e);
      window.setTimeout(() => setLoading(false), loadingMs);
    },
    [onClick, loadingMs]
  );

  const vars: Vars = {
    "--duration": `${duration}ms`,
    "--spin": `${spin}ms`,
    "--color": color,
  };

  return (
    <button
      type={type}
      className={styles.btn}
      style={vars}
      disabled={loading}
      onClick={handle}
    >
      <span className={styles.label} data-hidden={loading}>{children}</span>
      <span className={styles.spinner} data-visible={loading} aria-hidden="true" />
    </button>
  );
}