JSFiddle - React, Tailwind, and code Playground

HTML

<div class="boxy"></div><br/>
<div class="boxy"></div>

CSS

.boxy {
    width: 100px;
    height: 100px;
    background-color: black;
    border: 0px solid red;
    -webkit-transition: border 300ms ease 0s;
  -moz-transition: border 300ms ease 0s;
  -o-transition: border 300ms ease 0s;
  transition: border 300ms ease 0s;
}

.selected {
  border: 10px solid red;
}

JavaScript

$('.boxy').click(function(event){
	$(this).toggleClass('selected');
})