JSFiddle - React, Tailwind, and code Playground

HTML

<table>
<thead></thead>
<tbody>
<tr>
 <td> 1<input type="text" maxlength="1" oninput="focusNextElement(this)" id="a" name="a" tabeindex="1"></td>
 <td>3<input type="text" maxlength="1" oninput="focusNextElement(this)" id="b" name="b" tabeindex="3" disabled></td>
 <td>5<input type="text" maxlength="1" oninput="focusNextElement(this)" id="c" name="c" tabeindex="5">
</td></tr>
<tr>
 <td>2 <input type="text" maxlength="1" oninput="focusNextElement(this)" id="d" name="d" tabeindex="2"></td>
 <td>4<input type="text" maxlength="1" oninput="focusNextElement(this)" id="e" name="e" tabeindex="4"></td>
 <td>6<input type="text" maxlength="1" oninput="focusNextElement(this)" id="f" name="f"  tabeindex="6""></td>
</tr>
</tbody>
</table>

JavaScript

const inputs = document.querySelectorAll('input:not([disabled])')

function focusNextElement (input) {
  const nextIndex = [...inputs].findIndex(i => i === input) + 1
  if (inputs[nextIndex]) {
    inputs[nextIndex].focus()
  }
}