JSFiddle - React, Tailwind, and code Playground

HTML

<div class="flex numbers">
		<input type="checkbox" class="block bShadow-1">
		<input type="checkbox" class="block bShadow-2">
		<input type="checkbox" class="block bShadow-3">
		<input type="checkbox" class="block bShadow-4">
	</div>
  
<div class="result" id="result"></div>

	<script>
  // выводим нажатые блоки в поле result
		window.onload = function(){
			var items = document.querySelectorAll('.flex input');
			var result = document.querySelector('.result');

			for(var i = 0; i < items.length; i++){
				items[i].addEventListener("click", getShadow);
			}

			function getShadow(e){
				var styleItem = getComputedStyle(e.target);
				result.innerHTML = '.bshadow {<br>' + 
				'-webkit-box-shadow: ' + styleItem.boxShadow + '; <br>' +
				'-moz-box-shadow: ' + styleItem.boxShadow + '; <br>' +
				'box-shadow: ' + styleItem.boxShadow + ';<br>}';
			}
		}
	</script>

CSS

.flex {
  display: flex;
}
.block {
  position: relative;
  width: 100px;
  height: 100px;
  margin: 20px;
  border: 0;
  background: #fff !important;
}
.block::after {
  content: '';
  width: 100%;
  height: 100%;
  position: absolute;
  background-color: #fff;
}
.bShadow-1{-webkit-box-shadow:0px 1px 1px 1px rgba(0,0,0,0.06);-moz-box-shadow:0px 1px 1px 1px rgba(0,0,0,0.06);box-shadow:0px 1px 1px 1px rgba(0,0,0,0.06);}
.bShadow-2{-webkit-box-shadow:0 0 20px 0 rgba(150,150,150,.1);-moz-box-shadow:0 0 20px 0 rgba(150,150,150,.1);box-shadow:0 0 20px 0 rgba(150,150,150,.1);}
.bShadow-3{-webkit-box-shadow:0 20px 60px -10px rgba(0,0,0,.1);-moz-box-shadow:0 20px 60px -10px rgba(0,0,0,.1);box-shadow:0 20px 60px -10px rgba(0,0,0,.1);}
.bShadow-4{-webkit-box-shadow:0 15px 45px -9px rgba(0,0,0,0.25);-moz-box-shadow:0 15px 45px -9px rgba(0,0,0,0.25);box-shadow:0 15px 45px -9px rgba(0,0,0,0.25);}
/* выделяем полученные блоки по клику */
.result {
  border: 1px solid #dedede;
  -webkit-border-radius: .25rem;
  -moz-border-radius: .25rem;
  border-radius: .25rem;
  font-family: inherit;
  font-size: 1rem;
  line-height: inherit;
  min-width: 50%;
  display: inline-block;
  padding: 5px;
  min-height: 100px;

  -ms-user-select: all; 
  -moz-user-select: all; 
  -webkit-user-select: all; 
  user-select: all; 
}