title: Get data attribute of script tag?
body: <p>Say I've got the following script tag:</p>
  
  <pre><code>&lt;script async data-id="p3PkBtuA" src="//example.com/embed.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Within that <code>embed.js</code> file, how can I get the value of <code>data-id</code> attribute?</p>
  
  <p>I'm trying to keep the <code>embed.js</code> file as light as possible, so ideally it wouldn't need to use some sort of javascript library.</p>