title: How does Backbone.JS handle models with calculated attributes
body: <p>I'm using Backbone.JS with Mustache, so to render my tempaltes I call MyModel.toJSON(). This leaves me with only access to attributes. How can I have some attributes that are always calculated?</p>
  
  <p>I looked at the Backbone.JS documentation and it might work to override validate() but this seems like a hack and may lead to infinite loops.</p>
  
  <p>I also tried making an attribute be a function instead of a value, but Mustache doesn't get a value when I try to use it.</p>