CSS如何清除浮动

1. clearfix

.parent:after{
  content:'';
  display:bolck;
  clear:both;
}
.left{
  float:left
}
<div class="parent">
  <div class="left">123</div>
</div>

2. BFC overflow:hidden

.parent{
  overflow:hidden
}
.left{
  float:left
}
<div class="parent">
  <div class="left">123</div>
</div>