title: Coffeescript ||= analogue?
body: <p>I'm primarily a Rails developer, and so in whipping up a little script for my company's Hubot instance, I was hoping to accomplish the following:</p>
  
  <pre><code>robot.brain.data.contacts ||= {}
  </code></pre>
  
  <p>Or, only make this new hash if it doesn't already exist.  The idea being that I want to have a contacts array added dynamically through the script so I don't have to modify Hubot's source, and I obviously don't want to overwrite any contacts I add to it.</p>
  
  <p>Question: is there a quick little construct like the Rails ||= that I can use in Coffeescript to achieve the above goal?</p>
  
  <p>Cheers.</p>