JSFiddle - React, Tailwind, and code Playground

HTML

<form id="form">
  <input type="hidden" name="id" />
</form>
Result of using .id:
<div id="result">
</div>
<br>
Result of using getAttribute:
<div id="getAttributeResult">
</div>

JavaScript

element = document.getElementById('form');

document.getElementById('result').innerHTML = element.id
document.getElementById('getAttributeResult').innerHTML = element.getAttribute('id')