object.style.alignItems="center" - 尝试一下 - - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <style>
    div#main {
      width: 220px;
      height: 300px;
      border: 1px solid black;
      display: flex;
      align-items: center;
    }

    div#main div {
      flex: 1;
    }
  </style>
</head>
<body>

  <div id="main">
    <div style="background-color:coral;">红色</div>
    <div style="background-color:lightblue;">蓝色</div>
    <div style="background-color:lightgreen;">带有更多内容的绿色 div</div>
  </div>

  <p>点击“尝试一下”按钮，设置 alignItems 属性的值为 "flex-start"。</p>

  <button onclick="myFunction()">尝试一下</button>

  <script>
    function myFunction() {
      document.getElementById("main").style.alignItems = "flex-start";
    }
  </script>

  <p><b>注意：</b>Safari 不支持 alignItems 属性。</p>

</body>
</html>
        