title: Why does ++[[]][+[]]+[+[]] return the string "10"?
body: <p>This is valid and returns the string <code>"10"</code> in JavaScript (<a href="http://sla.ckers.org/forum/read.php?24,33349,33405" rel="noreferrer">more examples here</a>):</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>console.log(++[[]][+[]]+[+[]])</code></pre>
  </div>
  </div>
  </p>
  
  <p>Why? What is happening here?</p>