JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
<input type="text" id="myHiddenInput" placeholder="Введите количество">
<button id="myVisibleInput" class="fancybox">Попробовать на дня</button>
<p style="text-align: center;margin-bottom: 20px;" id="result"></p>

JavaScript

$("#myVisibleInput").click(function(){
	var res = $("#myHiddenInput").val();
	$("#result").text(res+" Дней")
});