JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button" style="width:300px;"><span style="text-align:left">selected all</span><span style="text-align:right;" class="caret"></span></button>

CSS

.caret {
  display: inline-block;
  width: 0;
  height: 0;
  margin-left: 2px;
  vertical-align: middle;
  border-top: 4px solid #000000;
  border-right: 4px solid transparent;
  border-bottom: 0 dotted;
  border-left: 4px solid transparent;
  content: "";    
}