JSFiddle - React, Tailwind, and code Playground

HTML

<div style="margin-top:30px;">
        <form action="index.php" method="post" id="doSite">
            <fieldset class="toggle">
                <input id="construction" name="construction" type="checkbox">
                <label for="construction">Site construction:</label>
                <span class="toggle-button"></span>
            </fieldset>
            
        </form>
    </div>

JavaScript

$('#construction').change(function() {
  $(this).closest("form").submit();
});

$('#doSite').submit(function() {
  alert("hey, the form was submitted");
  return false;
});