使用CSS对两行中的元素进行排序

<div class="container">
  <div class="item" style="order: 2;">元素2</div>
  <div class="item" style="order: 1;">元素1</div>
</div>

.container {
  display: flex;
  flex-direction: row;
}

.item {
  flex: 1;
}

<div class="container">
  <div class="item" style="grid-row: 2; grid-column: 1;">元素2</div>
  <div class="item" style="grid-row: 1; grid-column: 1;">元素1</div>
</div>

.container {
  display: grid;
  grid-template-rows: auto;
  grid-template-columns: auto;
}

.item {
  grid-row: auto;
  grid-column: auto;
}

<div class="container">
  <div class="item" style="float: right;">元素2</div>
  <div class="item" style="float: left;">元素1</div>
  <div style="clear: both;"></div>
</div>

.container {
  overflow: hidden;
}

.item {
  width: 50%;
}