title: Voting system with Backbone.js
body: <p>I have a <code>Book</code> model that has the property <code>upVotes</code>. <code>Book</code> instances can be queried from the database (MongoDB), modified, and then saved. If a user upvotes a book, I update the <code>upVotes</code> count, and save the whole model back to the server.</p>
  
  <p>The problem is that if someone else votes between the time the instance is loaded, and the time the instance is saved, then the two votes will be saved as just one vote. What I need is an easy way to say "increment the model by 1 server-side", instead of "increment the model by 1 client-side and hope there will be no conflict".</p>