JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li>1</li>
  <li>2</li>
  <li id="after" data-num="3">3</li>
  <li>4</li>
  <li>5</li>
  <li>6</li>
  <li>7</li>
  <li>8</li>
  <li>9</li>
  <li>10</li>
</ul>

CSS

.selected {
  color: red;
}

JavaScript

var src = $('#after');
 for (var i = 0, len = +src.data('num'); i < len; i++) {
   src = src.next("li").addClass('selected');
   if (!src.length) { break; }
 }