JSFiddle - React, Tailwind, and code Playground

HTML

<div id="nodes">
    <div class="error">This is error Node</div>  
    <div class="nextElement">This is next Element</div>
</div>

JavaScript

var nodes = Array.prototype.slice.call( document.getElementById('nodes').children ),
    errorNode = document.getElementsByClassName('error')[0];
var indexOfError = nodes.indexOf(errorNode);
var nextElement = nodes[indexOfError + 1];
console.log(nextElement);