showdownjs/test/extensions/google-prettify/basic.html

<p>Here's a simple hello world in javascript:</p>

<pre class="prettyprint linenums" tabIndex="0"><code data-inner="1">alert('Hello World!');
</code></pre>

<p>The <code class="prettyprint">alert</code> function is a build-in global from <code class="prettyprint">window</code>.</p>