JSFiddle - React, Tailwind, and code Playground

HTML

<div class=row>
    <div class="elem"></div>
    <div class="somediv2"></div>
    <div class="elem"></div>
    <div class="elem"></div>
    <div class="somediv3"></div>
    <div class="somediv4"></div>
        <div class="elem"></div>
    <div class="somediv3"></div>
    <div class="somediv4"></div>
        <div class="elem"></div>
    <div class="somediv3"></div>
    <div class="somediv4"></div>
<div class=row>

CSS

div { height: 30px; width: 200px; border: 1px solid black; }
div.elem { border: 2px solid red; }
div.new { border: 3px solid blue; }

JavaScript

$(document).ready( function () {
   $('.elem').each( function() {
     if($(this).next().hasClass('.elem')) {
         $('<div class="new"></div>').appendTo().prev('.places');
     } else {}
   });
});