JSFiddle - React, Tailwind, and code Playground

HTML

<div id="outer">
<table id="onlyTable">
    <tr>
      <td width="100%">
        <div></div>
      </td>
      <td width="5%">
        <div></div>
      </td>
    </tr>
</table>
</div>
<div id="showWidth"></div>

CSS

table, td {
    outline: solid 1px black;
    border-collapse: collapse;
}

#outer {
  width: 20000000px;
}

JavaScript

showWidth.innerHTML = onlyTable.offsetWidth + "px";