title: What does || {} means in JavaScript?
body: <p>I am confused with this code that I found in the Google Maps API:</p>
  
  <pre><code>window.google = window.google || {};
  google.maps = google.maps || {};
  </code></pre>
  
  <p>And other code that I saw in a book:</p>
  
  <pre><code>var QQ = QQ || {};
  </code></pre>
  
  <p>What does it mean?</p>
  
  <p>Why should we print that code at beginning of the JavaScript file?</p>