CSS3【display: flex;】与【flex-direction: 主轴方向;】的使用demo效果

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      list-style: none;
    }
    body {
      background-color: #eee;
      font-size: 22px;
    }
    h3 {
      margin: 10px;
      font-weight: normal;
    }
    section {
      width: 1000px;
      margin: 0 auto;
    }
    ul {
      background-color: #fff;
      border: 1px solid #ccc;
    }
    ul li {
      width: 200px;
      height: 200px;
      background-color: pink;
      margin: 10px;
    }

    /* 传统布局 */

    /* 清除浮动 */
    section:nth-child(1) ul {
      overflow: hidden;
    }
    section:nth-child(1) ul li {
      float: left;
    }

    /* 伸缩布局 */

    /* 设置伸缩盒子 */
    /* 
      display: flex; 默认主轴从左向右
      flex-direction: row(水平方向) row-reverse: 反转 column: 垂直方向  column-reverse: 反转列
     */
    section:nth-child(2) ul {
      display: flex;
    }
    section:nth-child(3) ul {
      display: flex;
      flex-direction: row;
    }
    section:nth-child(4) ul {
      display: flex;
      flex-direction: row-reverse;
    }
    section:nth-child(5) ul {
      display: flex;
      flex-direction: column;
    }
    section:nth-child(6) ul {
      display: flex;
      flex-direction: column-reverse;
    }
  </style>
</head>
<body>
  <section>
    <h3>传统布局</h3>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
  </section>
  <section>
    <h3>伸缩布局 display: flex;</h3>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
  </section>
  <section>
    <h3>主轴方向 flex-direction: row;</h3>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
  </section>
  <section>
    <h3>主轴方向 flex-direction: row-reverse;</h3>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
  </section>
  <section>
    <h3>主轴方向 flex-direction: column;</h3>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
  </section>
  <section>
    <h3>主轴方向 flex-direction: column-reverse;</h3>
    <ul>
      <li>1</li>
      <li>2</li>
      <li>3</li>
    </ul>
  </section>
</body>
</html>
demo 效果