JSFiddle - React, Tailwind, and code Playground

HTML

<div id="stage"></div>

JavaScript

data = {"success":false,"messages":{"firstname":["The firstname field is required."],"lastname":["The lastname field is required."]}};
if (!data['success']) {
     $.each(data['messages'], function(index, value) {
         $('#stage').append(value + '<br/>');
     });
}