title: How can I create an online JavaScript editor?
body: <p>I'm learning JavaScript. However, it's not so convenient to do some experiments. You have to create a template HTML file and then embed your JavaScript code into it, and then use a browser to open the
  HTML file, even you just want to see <code>alert(&quot;hello world&quot;)</code>.</p>
  <p>I wonder if it's easy to create an online JavaScript editor. The basic idea is: in a HTML text-area, you just type in JavaScript code directly, and it has one button, &quot;Run&quot;, below to run the JavaScript code.</p>
  <p>If it contains some syntax errors, maybe show the error message out. For example: someone already created one like this: <a href="http://www.codehouse.com/webmaster_tools/javascript_editor/" rel="nofollow noreferrer">http://www.codehouse.com/webmaster_tools/javascript_editor/</a></p>
  <p>How can I create this? Are there any materials, blog, etc. on how to create this?</p>