JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li class="active">
        <div class="course_video_heading"><span class="minus"></span> Introduction <div class="course_duration" align="right">1m 21s</div></div>
        <ul>
            <li class="course_video viewed">
                Welcome <div class="course_duration" align="right">1m 21s</div>
            </li>
            <li class="course_video viewed">
                I need to select this <div class="course_duration" align="right">1m 21s</div>
            </li>
        </ul>
    </li>
    <li>
        <div class="course_video_heading"><span class="plus"></span> Warm up <div class="course_duration" align="right">1h 15m</div></div>
        <ul>
            <li class="course_video viewed current">
                Roll down <div class="course_duration" align="right">57s</div>
            </li>
            <li class="course_video">
                Roll down with demi pointe variation <div class="course_duration" align="right">57s</div>
            </li>
            <li class="course_video" data-file="http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4" data-image="http://content.bitsontherun.com/thumbs/nPripu9l-480.jpg">
                Side roll down <div class="course_duration" align="right">57s</div>
            </li>
            <li class="course_video">
                Side roll down variation with contraction <div class="course_duration" align="right">57s</div>
            </li>
            <li class="course_video">
                Class exercise <div class="course_duration" align="right">57s</div>
            </li>
        </ul>
    </li>
    <li>
    </ul>

JavaScript

$('.current').parents('li').prev().find('li:last').css('border', '1px solid black');