JSFiddle - React, Tailwind, and code Playground

HTML

<div id='divBlock' style='display: none;'>text ...</div>
<input type='button' onClick=addCode() value='add'> 

Описание: <textarea id='textDescription' style='width:100%; height: 400px; ' name='description'> </textarea><br>

JavaScript

function addCode(id)
    {
         document.getElementById("textDescription").value = document.getElementById("textDescription").value + "&#010" + document.getElementById("divBlock).value;

    }