JSFiddle - React, Tailwind, and code Playground

HTML

<select name="id_tipo_contacto" id="id_tipo_contacto">
    <option value="empresa">Contacto empresa</option>
    <option value="casamento">Contacto casamento</option>
</select>
<div id="empresa" class="formulario">Mostra formulário empresa</div>
<div id="casamento" class="formulario" style="display:none;">Mostra formulário casamento</div>

JavaScript

var select = document.getElementById("id_tipo_contacto");
var formularios = document.querySelectorAll('.formulario');

select.onchange = function () {
    for (var i = 0; i < formularios.length; i++) formularios[i].style.display = 'none';
    var divID = select.options[select.selectedIndex].value;
    var div = document.getElementById(divID);
    div.style.display = 'block';
};