JSFiddle - React, Tailwind, and code Playground

HTML

<div data-chart="1">
  <div class="chart" data-before='50%'><span> Completed</span></div>
</div>

CSS

[data-chart="1"] .chart:before {
  content: attr(data-before);
}

JavaScript

$('[data-chart=1] .chart').attr('data-before', '100%');