JSFiddle - React, Tailwind, and code Playground
HTML
<div class="modal-body" client-name="test1">
<input class="gform_hidden"/>
</div>
<div class="modal-body" client-name="new name">
<input class="gform_hidden"/>
</div>
<div class="modal-body" client-name="test3">
<input class="gform_hidden"/>
</div>
JavaScript
$('.modal-body').each(function() {
var cname = $(this).attr('client-name');
$('input.gform_hidden').val(cname);
});