JSFiddle - React, Tailwind, and code Playground

HTML

<div class="triangle">
    向上的三角
</div>
<br />
<div class="rightTriangle">
    向右的三角
</div>
<br />
<div>例子：</div>
<div class="issue">Issue<em>15</em></div>
<a href="http://www.camnpr.com/">更多访问...</a>

CSS

.triangle, .rightTriangle{background-color:#000;width:50px;height:100px;color:#fff;}
.triangle:after{content:'';display:block; border:25px solid transparent; border-bottom:21px solid #fff;border-top:none}

.rightTriangle:after{content:'';display:block;border-top: 5px solid transparent;
border-bottom: 5px solid transparent; border-left: 15px solid #fff;}

/*case*/
.issue {
	position: absolute;
	top: 0;
	right: 90px;
	width: 48px;
	height: 58px;
	font-family: Georgia;
	background: #649F0C;
	text-align: center;
	font-size: 15px;
	line-height: 1.2;
	padding-top:6px;
} 
.issue:after {
	content: ''; 
	display: block;
	position: absolute;
	width: 0px;
	height: 0px;
	bottom: 0;
	left: 0;
	border: 27px solid transparent;
	border-bottom: 15px solid #fff; /*此颜色根据页面背景色一直。不能为透明色transparent*/
	border-top: none;
	z-index: 1;
}  
.issue em {
	display: block;
	font-style: normal;
	font-size: 18px;
}