JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="selectables">
  <li><img src="//dummyimage.com/100x100">
  <li><img src="//dummyimage.com/100x100">
  <li><img src="//dummyimage.com/100x100">
  <li><img src="//dummyimage.com/100x100">
</ul>

CSS

ul.selectables li {
  display:inline-block;
  margin:1em;
}

ul.selectables img.selected {
  outline:solid 2px red;
}

JavaScript

addEventListener('load', ()=>{
	const list = document.querySelector( 'ul.selectables' );
  list.addEventListener('click', (event)=>{
  	const image = event.target;
    image.classList.toggle('selected');
  });
});