JSFiddle - React, Tailwind, and code Playground

HTML

<div class="foo"></div>

CSS

.foo {
    margin-left:20px;
}

.foo:before {
    content: ' ';
	  height: 0;
	  position: absolute;
	  width: 0;
	  border: 10px solid transparent;
	  border-left-color: #333;
}