[スニペット]HTML&CSS&JSポップアップ


```html
<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>ポップアップ表示</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>
  <button id="openPopup">ポップアップを開く</button>

  <div id="popupOverlay" class="overlay">
    <div class="popup">
      <h2>ポップアップ画面</h2>
      <p>これは簡単なポップアップ画面です。</p>
      <button id="closePopup">閉じる</button>
    </div>
  </div>

  <script src="script.js"></script>
</body>
</html>
```
```css
body {
  font-family: Arial, sans-serif;
}

button {
  padding: 10px 20px;
  font-size: 16px;
  cursor: pointer;
}

/* オーバーレイ */
.overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: rgba(0, 0, 0, 0.5);
  justify-content: center;
  align-items: center;
}

/* ポップアップウィンドウ */
.popup {
  background: white;
  padding: 20px;
  border-radius: 8px;
  width: 300px;
  box-shadow: 0 10px 25px rgba(0,0,0,0.2);
}

h2 {
  margin-top: 0;
}
```
```js
const openPopupButton = document.getElementById('openPopup');
const closePopupButton = document.getElementById('closePopup');
const popupOverlay = document.getElementById('popupOverlay');

openPopupButton.addEventListener('click', () => {
  popupOverlay.style.display = 'flex';
});

closePopupButton.addEventListener('click', () => {
  popupOverlay.style.display = 'none';
});
```
ポップアップに装飾を付ける
```css
body {
  font-family: 'Helvetica Neue', sans-serif;
  background: #f5f5f5;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.open-btn {
  padding: 12px 24px;
  background: #007bff;
  color: white;
  font-size: 16px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  box-shadow: 0 4px 10px rgba(0, 123, 255, 0.2);
  transition: background 0.3s ease;
}

.open-btn:hover {
  background: #0056b3;
}

.overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: rgba(0, 0, 0, 0.6);
  justify-content: center;
  align-items: center;
  animation: fadeIn 0.3s ease forwards;
}

.popup {
  background: white;
  padding: 30px;
  border-radius: 16px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
  position: relative;
  max-width: 90%;
  width: 400px;
  animation: slideUp 0.3s ease;
  text-align: center;
}

h2 {
  margin-top: 0;
  font-size: 24px;
  color: #333;
}

p {
  color: #555;
  margin-bottom: 0;
}

.close-btn {
  position: absolute;
  top: 12px;
  right: 16px;
  background: none;
  border: none;
  font-size: 28px;
  color: #888;
  cursor: pointer;
  transition: color 0.2s;
}

.close-btn:hover {
  color: #333;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideUp {
  from {
    transform: translateY(30px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}
```

```
<div id="popupOverlay" class="overlay">
  <div class="popup">
    <div class="popup-header">
      <h2>お知らせ</h2>
    </div>
    <div class="popup-body">
      <p>これはスタイリッシュなポップアップ画面です。ご確認ください。</p>
    </div>
    <button id="closePopup" class="close-btn">&times;</button>
  </div>
</div>
```
```
.popup {
  background: white;
  border-radius: 16px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
  position: relative;
  max-width: 90%;
  width: 400px;
  overflow: hidden; /* ← ヘッダーの角丸を維持するために追加 */
  animation: slideUp 0.3s ease;
}

/* ヘッダー部分に色をつける */
.popup-header {
  background: #007bff;
  color: white;
  padding: 16px;
  text-align: center;
}

/* 本文部分を分離 */
.popup-body {
  padding: 24px;
  text-align: center;
  color: #555;
}

/* 既存の h2 スタイルは不要になる場合も */
.popup-header h2 {
  margin: 0;
  font-size: 20px;
}

/* close ボタンは上部の右端に置く */
.close-btn {
  position: absolute;
  top: 10px;
  right: 16px;
  background: none;
  border: none;
  font-size: 28px;
  color: #fff;
  cursor: pointer;
  transition: color 0.2s;
}

.close-btn:hover {
  color: #ddd;
}
```