JSFiddle - React, Tailwind, and code Playground

HTML

Click the big box<br/>

<div id='inputBox' class='path1'></div>
<div id='pathToOut' class='path1'></div>
<div id='outputBox' class='path1'></div>

CSS

#inputBox {
	width:50px;
	height:50px;
	border:3px solid darkgrey;
	background-color:#eeeeee;
}

#pathToOut {
	border:3px solid darkgrey;
	width:100px;
	height:0px;
	position:relative;
	top:-30px;
	left:55px;
}

#outputBox {
	width:30px;
	height:30px;

	border:3px solid darkgrey;
	background-color:#eeeeee;

	position:relative;
	top:-52px;
	left:150px;
}

JavaScript

function lightPath() {

		// get class of clicked item
		var itemClass = this.className; // eg. 'path1'

		// get all elements with same class
		var pathElems = document.body.getElementsByClassName('path1');

		// go through each element and change its border color etc..
		for(var x = 0; x < pathElems.length; x++) {
			pathElems[x].style.borderColor = 'orange';
		}
	}


	document.getElementById('inputBox').onclick = lightPath;