在父级上使用 transform:scale 时，子元素的下拉菜单位于另一行下方答案

【问题标题】：When using transform:scale on parent, child element's dropdown goes under another row在父级上使用 transform:scale 时，子元素的下拉菜单位于另一行下方
【发布时间】：2020-01-16 04:13:24
【问题描述】：

所以问题是，当我试图在悬停时缩放我的行时，如果我的下拉菜单打开，我的下拉菜单会位于下一行。

如何让它保持领先？

我尝试过 z-index，但没有任何帮助。使用比例尺可能有一些我不明白的地方。

.row {
  background: #f8f9fa;
  margin-top: 5px;
}

.col {
  border: solid 1px #6c757d;
  padding: 10px;
}

.myScale1:hover {
  transform: scale(1.05);
}

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<!-- 
  Bootstrap docs: https://getbootstrap.com/docs
-->

<div class="container">
  <div class="row myScale1">
    <div class="col ">
      1 of 2
    </div>
    <div class="col">
      <div class="dropdown">
        <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
          Dropdown button
        </button>
        <div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <a class="dropdown-item" href="#">Something else here</a>
        </div>
      </div>
    </div>
  </div>
  <div class="row">
    <div class="col">
      1 of 2
    </div>
    <div class="col">
      2 of 2
    </div>
  </div>
  <div class="row">
    <div class="col">
      1 of 2
    </div>
    <div class="col">
      2 of 2
    </div>
  </div>
</div>

【问题讨论】：

标签： javascript css bootstrap-4

【解决方案1】：

使用transform 将创建一个堆叠上下文，在其中创建下拉菜单，因此所有行（堆叠上下文）都将被绘制顺序之后的下一行隐藏。

为避免这种情况，只需增加缩放行的z-index：

.row {
  background: #f8f9fa;
  margin-top: 5px;
}

.col {
  border: solid 1px #6c757d;
  padding: 10px;
}

.myScale1:hover {
  transform: scale(1.05);
  position:relative;
  z-index:1;
}

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<!-- 
  Bootstrap docs: https://getbootstrap.com/docs
-->

<div class="container">
  <div class="row myScale1">
    <div class="col ">
      1 of 2
    </div>
    <div class="col">
      <div class="dropdown">
        <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
          Dropdown button
        </button>
        <div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <a class="dropdown-item" href="#">Something else here</a>
        </div>
      </div>
    </div>
  </div>
  <div class="row">
    <div class="col">
      1 of 2
    </div>
    <div class="col">
      2 of 2
    </div>
  </div>
  <div class="row">
    <div class="col">
      1 of 2
    </div>
    <div class="col">
      2 of 2
    </div>
  </div>
</div>

有关绘画顺序和堆叠上下文的更多详细信息的相关问题：

Why can't an element with a z-index value cover its child?

【讨论】：