JSFiddle - React, Tailwind, and code Playground

HTML

<div id="divBlock" style="display: none;">text ...</div>
<input type="button" onclick="addCode();return false" value="add"> 

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

<script>
function addCode(){
return document.getElementById("textDescription").value += "&#010" + document.getElementById("divBlock").innerHTML;
}
</script>