<!doctype html>
<html lang="en">
<head>
<title>JavaScript Editor</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta charset="utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
</head>
<body onload="$('#page').html(localStorage.html)">
<button onclick="document.all.html.innerText=localStorage.html;document.all.editor.style.display='inline'">edit</button>
<div style="display: none;" id="editor">
<button onclick="localStorage.html=document.all.html.innerText;location.reload()">save and reload</button>
<br>
<div id="html" contenteditable="true" style="border: 1px solid black;padding: 10px;"></div>
</div>
<div id="page"></div>
</body>
</html>