JSFiddle - React, Tailwind, and code Playground
by Alfie
HTML
<form id="userForm" action="xpto">
<input type="text" name="form[data_nascimento_beneficiario_1]" value="testing" />
<input type="submit" value="Continuar" />
</form>
JavaScript
alert($('input[name="form[data_nascimento_beneficiario_1]"]').length);