JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
</head>
<body>

<table>
  <tr>
    <td style="border:1px solid black;height:300px;width:100px">A</td>
    <td style="border:1px solid black;height:100%">
      <div style="border:1px solid blue;height:100%;width:100px">B</div>
    </td>
  </tr>
</table>

</body>
</html>

JavaScript

$('table td:eq(1) div').height($('table td:eq(1)').height());