JSFiddle - React, Tailwind, and code Playground

HTML

<div class="target">
    
</div>

CSS

.red {
    color: red
}

JavaScript

$('.target').append('<span class="red">New span</span>');
$('head').append(
  $('<style/>', {
    id : 'mystyle',
    html : '.red {color: purple }'
  })
);
$('#mystyle').append(' .someother { color: green; font-size: 13px } ');
$('.target').append('<span class="red">New span</span>');
$('.target').append('<span class="someother ">Someother New span</span>');