JSFiddle - React, Tailwind, and code Playground

HTML

<div class="WorkingHours">
M,W,Th,F 7:30 AM - 4:00 PM<br />Tu 7:30 AM - 6:00 PM<br />
</div>

JavaScript

// still better to do:
$('.WorkingHours')
 .find('br').last().replaceWith('.')
 .end().replaceWith(' ');