<div class="top"></div>
css实现上箭头
.top {
width:;
height:;
border-left: 10px solid transparent;
border-right: 10px solid transparent;
border-bottom: 10px solid #217AFF;
}
css实现下箭头
.top {
width:;
height:;
border-left: 10px solid transparent;
border-right: 10px solid transparent;
border-top: 10px solid #217AFF;
}