title: Default getter value in Javascript
body: <p>I'd like to set a default return value for an object.</p>
  
  <p>If I have a set up like in the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_setters" rel="nofollow noreferrer">moz docs</a></p>
  
  <pre><code>var o = { a: 0 };
  
  Object.defineProperties(o, {
      'b': { get: function() { return this.a + 1; } },
      'c': { set: function(x) { this.a = x / 2; } }
  });
  </code></pre>
  
  <p>What I want is to define a default such that when we try <code>o[unexpectedVar]</code> it returns our default value.</p>
  
  <p>Is this possible with the sort of set up above?</p>