JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box1"></div>
<div class="box9"></div>
<div class="box4"></div>
<div class="test">

</div>

JavaScript

var maximum = null;

$('.a').each(function() {
  var value = parseFloat($(this).attr('x'));
  maximum = (value > maximum) ? value : maximum;
});

$('.test').text(maxiumun);