d-block

bootstrap5.css

bootstrap5.css
.d-block {
  display: block !important;
}
bootstrap5.css
@media (min-width: 768px) {
  .float-md-start {
    float: left !important;
  }
  .float-md-end {
    float: right !important;
  }
  .float-md-none {
    float: none !important;
  }
  .d-md-inline {
    display: inline !important;
  }
  .d-md-inline-block {
    display: inline-block !important;
  }
  .d-md-block {
    display: block !important;
  }
  .d-md-grid {
    display: grid !important;
  }
  .d-md-table {
    display: table !important;
  }
  .d-md-table-row {
    display: table-row !important;
  }
  .d-md-table-cell {
    display: table-cell !important;
  }
  .d-md-flex {
    display: flex !important;
  }
  .d-md-inline-flex {
    display: inline-flex !important;
  }
  .d-md-none {
    display: none !important;
  }
  .flex-md-fill {
    flex: 1 1 auto !important;
  }
  .flex-md-row {
    flex-direction: row !important;
  }
  .flex-md-column {
    flex-direction: column !important;
  }
  .flex-md-row-reverse {
    flex-direction: row-reverse !important;
  }
  .flex-md-column-reverse {
    flex-direction: column-reverse !important;
  }
  .flex-md-grow-0 {
    flex-grow: 0 !important;
  }
  .flex-md-grow-1 {
    flex-grow: 1 !important;
  }
  .flex-md-shrink-0 {
    flex-shrink: 0 !important;
  }
  .flex-md-shrink-1 {
    flex-shrink: 1 !important;
  }
  .flex-md-wrap {
    flex-wrap: wrap !important;
  }
  .flex-md-nowrap {
    flex-wrap: nowrap !important;
  }
  .flex-md-wrap-reverse {
    flex-wrap: wrap-reverse !important;
  }
  .gap-md-0 {
    gap: 0 !important;
  }
  .gap-md-1 {
    gap: 0.25rem !important;
  }
  .gap-md-2 {
    gap: 0.5rem !important;
  }
  .gap-md-3 {
    gap: 1rem !important;
  }
  .gap-md-4 {
    gap: 1.5rem !important;
  }
  .gap-md-5 {
    gap: 3rem !important;
  }
  .justify-content-md-start {
    justify-content: flex-start !important;
  }
  .justify-content-md-end {
    justify-content: flex-end !important;
  }
  .justify-content-md-center {
    justify-content: center !important;
  }
  .justify-content-md-between {
    justify-content: space-between !important;
  }
  .justify-content-md-around {
    justify-content: space-around !important;
  }
  .justify-content-md-evenly {
    justify-content: space-evenly !important;
  }
  .align-items-md-start {
    align-items: flex-start !important;
  }
  .align-items-md-end {
    align-items: flex-end !important;
  }
  .align-items-md-center {
    align-items: center !important;
  }
  .align-items-md-baseline {
    align-items: baseline !important;
  }
  .align-items-md-stretch {
    align-items: stretch !important;
  }
  .align-content-md-start {
    align-content: flex-start !important;
  }
  .align-content-md-end {
    align-content: flex-end !important;
  }
  .align-content-md-center {
    align-content: center !important;
  }
  .align-content-md-between {
    align-content: space-between !important;
  }
  .align-content-md-around {
    align-content: space-around !important;
  }
  .align-content-md-stretch {
    align-content: stretch !important;
  }
  .align-self-md-auto {
    align-self: auto !important;
  }
  .align-self-md-start {
    align-self: flex-start !important;
  }
  .align-self-md-end {
    align-self: flex-end !important;
  }
  .align-self-md-cent

html bootstrap5 Sample

rowとcolの行の分割をブレイクポイントで切り替える：d-none d-md-block

col
col
col
col
  <div class="row">
    <div class="col">col</div>
    <div class="col">col</div>
    <div class="w-100 d-none d-md-block"></div>
    <!-- Medium以上では{dsplay:block}、未満では{display:none} -->
    <div class="col">col</div>
    <div class="col">col</div>
  </div>

背景に色を付ける：bg-primary

bg-primary

bg-secondary

bg-success

bg-danger

bg-warning

bg-info

bg-light

bg-dark

bg-white

bg-transparent

  <div class="text-center">
    <p><a href="#" class="bg-primary text-white d-block py-2">bg-primary</a></p>
    <p><a href="#" class="bg-secondary text-white d-block py-2">bg-secondary</a></p>
    <p><a href="#" class="bg-success text-white d-block py-2">bg-success</a></p>
    <p><a href="#" class="bg-danger text-white d-block py-2">bg-danger</a></p>
    <p><a href="#" class="bg-warning text-dark d-block py-2">bg-warning</a></p>
    <p><a href="#" class="bg-info text-white d-block py-2">bg-info</a></p>
    <p><a href="#" class="bg-light text-dark d-block py-2">bg-light</a></p>
    <p><a href="#" class="bg-dark text-white d-block py-2">bg-dark</a></p>
    <p><a href="#" class="bg-white text-dark d-block py-2">bg-white</a></p>
    <p><a href="#" class="bg-transparent d-block py-2">bg-transparent</a></p>
  </div>

ブロック表示のspan：d-block

ブロック表示のspan ブロック表示のspan 
  <span class="d-block bg-primary text-white">ブロック表示のspan</span>
  <span class="d-block bg-dark text-white">ブロック表示のspan</span>

画像の中央寄せ：mx-autoとd-block

中央寄せ画像 
  <!-- imgにclassを設定する -->
  <img src="https://via.placeholder.com/200x200" class="mx-auto d-block" alt="中央寄せ画像">

js カルーセル基本的な使用例：carousel slideとdata-bs-ride

First slide
Second slide
Third slide 
  <div class="container">
    <!-- 複数の画像を用意して、回転木馬のように自動で切り替えていく -->
    <!-- slideさせていく -->
    <div class="carousel slide" data-bs-ride="carousel">
      <div class="carousel-inner">
        <div class="carousel-item active">
          <img class="d-block w-100" alt="First slide"
            src="https://via.placeholder.com/1600x900/FFFF00/000000?text=First slide">
        </div>
        <div class="carousel-item">
          <img class="d-block w-100" alt="Second slide"
            src="https://via.placeholder.com/1600x900/FFFF00/000000?text=Second slide">
        </div>
        <div class="carousel-item">
          <img class="d-block w-100" alt="Third slide"
            src="https://via.placeholder.com/1600x900/FFFF00/000000?text=Third slide">
        </div>
      </div>
    </div>
  </div>

js インジケータ、タイトル、キャプション付きカルーセル：carousel-indicatorsとdata-bs-slide-to

  <div id="carouselSample" class="carousel slide" data-bs-ride="carousel">
    <!-- インジケーターによるフェード遷移（好きな場所にクリックでいける） -->
    <ol class="carousel-indicators">
      <li data-bs-target="#carouselSample" data-bs-slide-to="0" class="active"></li>
      <li data-bs-target="#carouselSample" data-bs-slide-to="1"></li>
      <li data-bs-target="#carouselSample" data-bs-slide-to="2"></li>
    </ol>
    <!-- カルーセル部分 -->
    <div class="carousel-inner">
      <div class="carousel-item active">
        <img class="d-block w-100" slide"
          src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=First slide">
        <div class="carousel-caption d-none d-md-block">
          <h5>スライドタイトル</h5>
          <p>スライドのキャプション</p>
        </div>
      </div>
      <div class="carousel-item">
        <img class="d-block w-100" alt="img"
          src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=Second slide">
        <div class="carousel-caption d-none d-md-block">
          <h5>スライドタイトル</h5>
          <p>スライドのキャプション</p>
        </div>
      </div>
      <div class="carousel-item">
        <img class="d-block w-100" alt="img"
          src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=Third slide">
        <div class="carousel-caption d-none d-md-block">
          <h5>スライドタイトル</h5>
          <p>スライドのキャプション</p>
        </div>
      </div>
    </div>
    <!-- コントローラー部分 -->
    <!-- 前と次のアイコン付きカルーセル -->
    <a class="carousel-control-prev" href="#carouselSample" role="button" data-bs-slide="prev">
      <span class="carousel-control-prev-icon" aria-hidden="true"></span>
      <span class="visually-hidden">前に戻る</span>
    </a>
    <a class="carousel-control-next" href="#carouselSample" role="button" data-bs-slide="next">
      <span class="carousel-control-next-icon" aria-hidden="true"></span>
      <span class="visually-hidden">次に送る</span>
    </a>
  </div>

js データ属性でインターバルの設定：data-bs-interval

  <div class="container">
    <!-- intervalの設定 -->
    <div id="carouselExample" class="carousel slide" data-bs-ride="carousel" data-bs-interval="15000">
      <ol class="carousel-indicators">
        <li data-bs-target="#carouselExample" data-bs-slide-to="0" class="active"></li>
        <li data-bs-target="#carouselExample" data-bs-slide-to="1"></li>
        <li data-bs-target="#carouselExample" data-bs-slide-to="2"></li>
      </ol>
      <!-- カルーセル部分 -->
      <div class="carousel-inner">
        <!-- First slide -->
        <div class="carousel-item active"> <img class="d-block w-100" alt="img"
            src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=First slide">
          <div class="carousel-caption">
            <h5>スライドタイトル</h5>
            <p>スライドのキャプション</p>
          </div>
        </div>
        <!-- Second slide -->
        <div class="carousel-item"> <img class="d-block w-100" alt="img"
            src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=Second slide">
          <div class="carousel-caption">
            <h5>スライドタイトル</h5>
            <p>スライドのキャプション</p>
          </div>
        </div>
        <!-- Third slide -->
        <div class="carousel-item"> <img class="d-block w-100" alt="img"
            src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=Third slide">
          <div class="carousel-caption">
            <h5>スライドタイトル</h5>
            <p>スライドのキャプション</p>
          </div>
        </div>
      </div>
      <!-- 前に戻るアイコン -->
      <a class="carousel-control-prev" href="#carouselExample" role="button" data-bs-slide="prev">
        <span class="carousel-control-prev-icon" aria-hidden="true"></span>
        <span class="visually-hidden">前に戻る</span>
      </a>
      <!-- 次に送るアイコン -->
      <a class="carousel-control-next" href="#carouselExample" role="button" data-bs-slide="next">
        <span class="carousel-control-next-icon" aria-hidden="true"></span>
        <span class="visually-hidden">次に送る</span>
      </a>
    </div>
  </div>

js データ属性でフェードトランジションの設定：carousel-fade

  <div class="container">
    <!-- スライドの代わりにフェードトランジションでスライドをアニメーションさせる -->
    <div id="carouselExample" class="carousel slide carousel-fade" data-bs-ride="carousel">
      <ol class="carousel-indicators">
        <li data-bs-target="#carouselExample" data-bs-slide-to="0" class="active"></li>
        <li data-bs-target="#carouselExample" data-bs-slide-to="1"></li>
        <li data-bs-target="#carouselExample" data-bs-slide-to="2"></li>
      </ol>
      <!-- カルーセル部分 -->
      <div class="carousel-inner">
        <!-- First slide -->
        <div class="carousel-item active"> <img class="d-block w-100" alt="img"
            src="https://via.placeholder.com/1600x900/666666/FFFF00/000000?text=First slide">
          <div class="carousel-caption">
            <h5>スライドタイトル1</h5>
            <p>スライドのキャプション3</p>
          </div>
        </div>
        <!-- Second slide -->
        <div class="carousel-item"> <img class="d-block w-100" alt="img"
            src="https://via.placeholder.com/1600x900/665566/FF0000/000000?text=Second slide">
          <div class="carousel-caption">
            <h5>スライドタイトル2</h5>
            <p>スライドのキャプション3</p>
          </div>
        </div>
        <!-- Third slide -->
        <div class="carousel-item"> <img class="d-block w-100" alt="img"
            src="https://via.placeholder.com/1600x900/664466/FFEE00/000000?text=Third slide">
          <div class="carousel-caption">
            <h5>スライドタイトル3</h5>
            <p>スライドのキャプション3</p>
          </div>
        </div>
      </div>
      <!-- 前に戻るアイコン -->
      <a class="carousel-control-prev" href="#carouselExample" role="button" data-bs-slide="prev">
        <span class="carousel-control-prev-icon" aria-hidden="true"></span>
        <span class="visually-hidden">前に戻る</span>
      </a>
      <!-- 次に送るアイコン -->
      <a class="carousel-control-next" href="#carouselExample" role="button" data-bs-slide="next">
        <span class="carousel-control-next-icon" aria-hidden="true"></span>
        <span class="visually-hidden">次に送る</span>
      </a>
    </div>
  </div>

js インジケーター、キャプションを暗くする：carousel-dark

  <div id="carouselExampleDark" class="carousel carousel-dark slide" data-bs-ride="carousel">
    <ol class="carousel-indicators">
      <li data-bs-target="#carouselExampleDark" data-bs-slide-to="0" class="active"></li>
      <li data-bs-target="#carouselExampleDark" data-bs-slide-to="1"></li>
      <li data-bs-target="#carouselExampleDark" data-bs-slide-to="2"></li>
    </ol>
    <div class="carousel-inner">
      <div class="carousel-item active" data-bs-interval="10000">
        <svg class="bd-placeholder-img bd-placeholder-img-lg d-block w-100" width="800" height="400"
          xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Placeholder: First slide"
          preserveAspectRatio="xMidYMid slice" focusable="false">
          <title>image svg 1</title>
          <rect width="100%" height="100%" fill="#f5f5f5" /><text x="50%" y="50%" fill="#aaa" dy=".3em">First
            slide</text>
        </svg>
        <div class="carousel-caption d-none d-md-block">
          <h5>First タイトル</h5>
          <p>First xxxxxxxxxxxxxx</p>
        </div>
      </div>
      <div class="carousel-item" data-bs-interval="2000">
        <svg class="bd-placeholder-img bd-placeholder-img-lg d-block w-100" width="800" height="400"
          xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Placeholder: Second slide"
          preserveAspectRatio="xMidYMid slice" focusable="false">
          <title>image svg 2</title>
          <rect width="100%" height="100%" fill="#eee" /><text x="50%" y="50%" fill="#bbb" dy=".3em">Second
            slide</text>
        </svg>
        <div class="carousel-caption d-none d-md-block">
          <h5>Second タイトル</h5>
          <p>Second xxxxxxxxxxxxxx</p>
        </div>
      </div>
      <div class="carousel-item">
        <svg class="bd-placeholder-img bd-placeholder-img-lg d-block w-100" width="800" height="400"
          xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Placeholder: Third slide"
          preserveAspectRatio="xMidYMid slice" focusable="false">
          <title>image svg 3</title>
          <rect width="100%" height="100%" fill="#e5e5e5" /><text x="50%" y="50%" fill="#999" dy=".3em">Third
            slide</text>
        </svg>
        <div class="carousel-caption d-none d-md-block">
          <h5>Third タイトル</h5>
          <p>Third xxxxxxxxxxxxxx</p>
        </div>
      </div>
    </div>
    <a class="carousel-control-prev" href="#carouselExampleDark" role="button" data-bs-slide="prev">
      <span class="carousel-control-prev-icon" aria-hidden="true">
        <span class="visually-hidden">Previous
    </a>
    <a class="carousel-control-next" href="#carouselExampleDark" role="button" data-bs-slide="next">
      <span class="carousel-control-next-icon" aria-hidden="true">
        <span class="visually-hidden">Next
    </a>
  </div>