View 代码

  <div class="mas-view">
    <div class="m-2">
      <span>新新消息消新消息消息新消息新消息新消息新消息新消息新消息新消息新消息新息</span>
    </div>
   </div>

CSS 样式

.mas-view{
  width: 100%;
  height: auto;
  border: 1px solid #000000;
  position: relative;
  margin: 12px 0px;
}
.mas-view::after{
  content: "";
  position: absolute;
  width: 0px;
  height: 0px;
  left: 180px;
  top: -20px;
  border: 10px solid transparent;
  border-bottom: 10px solid #000000;
}
.mas-view::before{
  content: "";
  position: absolute;
  width: 0px;
  height: 0px;
  top: -19px;
  left: 180px;
  z-index: 1;
  border: 10px solid transparent;
  border-bottom: 10px solid #fff;  
}