JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
   <fieldset class="inner"></fieldset>
   <fieldset class="inner first_name"></fieldset>
   <fieldset class="inner last_name"></fieldset>
   <fieldset class="inner user"></fieldset>
   <fieldset class="inner password"></fieldset>
   <fieldset class="inner"></fieldset>
   <fieldset class="inner avatar"></fieldset>
   <fieldset class="inner submit"></fieldset>
</div>

CSS

.inner-left { margin: 10px; }
.inner-middle { margin: 10px; }
.inner-right { margin: 10px; }

JavaScript

$('.inner:lt(5)').wrapAll($('<div>').addClass('inner-left'));
$('.inner:gt(4):lt(2)').wrapAll($('<div>').addClass('inner-middle'));
$('.inner:gt(6)').wrapAll($('<div>').addClass('inner-right'));