What does !!~ do?
<p>I was reading <a href="http://robertpitt.me/2012/09/5-tips-for-nodejs-in-production-mode/">this blog post</a> which mentioned using:</p>

<pre><code>!!~ 
</code></pre>

<p>I have no idea what this does? at first I thought it would give an error, but the code below does run:</p>

<pre><code>var _sessions = [
    "_SID_1",
    "_SID_2",
    "_SID_3",
    "_SID_4"
];

if(!!~_sessions.indexOf("_SID_5")) {
    console.log('found');
} else {
    console.log('!found');
}
</code></pre>

<p>output:</p>

<pre><code>node test.js 
!found
</code></pre>
