title: What are the benefits and drawbacks of using the 'this' keyword in a constructor function over the prototype property?
body: <p>In the following code I instantiate an object and it inherits properties in two completely different ways.   </p>
  
  <pre><code>function C(){
      this.k1 = "v1";
  }
  C.prototype.k2 = "v2";
  var o = new C;
  </code></pre>
  
  <p>The first (k1) seems to attach to the instantiated object (o) as an 'own' property, the second (k2) does not attach to anything in the instantiated object but seems to just access it's value through the _ _ proto _ _ property (or [[prototype]]).  In a way it seems like the first way is analogous to (in every computing) making a 'copy' of a file on your desktop whereas the second way is analogous to making an 'alias' of a file on your desktop, and of course, in this analogy I'm makin 'files' are analogous to 'properties'. </p>
  
  <p>I'm wondering if this is the correct way of imagining what's taking place and if so what the benefits and drawbacks are to using one method over the other.  I'm assuming that using the prototype property saves memory because it doesn't force the newly instantiated object (o) to have keys (k1) as an 'own' property, but maybe I'm wrong.</p>
  
  <p>Why would anyone choose one method over another?</p>