backbone-view.js

initialize: function() {
  // Observe changes to the model and call the render function when they happen
  this.model.on('change', this.render, this);

  // Render the view for the first time
  render();
}

userMarkedObjectAsFavorite: function() {
  // We're changing the mode, not the UI
  this.model.set('favorite', true);
}

render: function() {
  // Code to update the UI from the model
}

// Un-observing code is left out to simplify the example