Monkey patch `Backbone.Model.extend()` with ES5 getters/setters for each attribute defined in the defaults.

backbone.model.es5properties.js

/**
 * Monkey patch `Backbone.Model.extend()` with ES5 getters/setters for each
 * attribute defined in the defaults. Gives you the added bonus of being
 * to pass your backbone models directly to your Mustache.js views.
 *
 * Example:
 *
 * var User = Backbone.Model.extend({
 *   defaults: {
 *     username: undefined,
 *     email: undefined
 *   }
 * });
 * 
 * // Now, instead of `user.set(...)`, we can user attribute names at properties:
 * var user = new User();
 * user.username = "dandean"
 * user.email = "punch@face.com"
 * 
 * JSON.stringify(user);
 * // -> "{"username":"dandean","email":"punch@face.com"}"
**/

// Store original Backbone.Model.extend for later use...
var originalBackboneModelExtend = Backbone.Model.extend;

// Define a NEW Backbone.Model.extend which will place getters and setters
// for each of our defaults on the model instance prototype...
Backbone.Model.extend = function(parent, protoProps, staticProps) {
  // Call the original extend method...
  var child = originalBackboneModelExtend.call(Backbone.Model, parent, protoProps, staticProps);
  
  // Swap arguments, if parent wasn't provided...
  if (parent instanceof Backbone.Model === false) {
    protoProps = parent;
  }

  // If defaults are provided...
  if ('defaults' in protoProps) {
    Object.keys(protoProps.defaults).forEach(function(name) {
      // Unless the property is id...
      if (name != 'id') {
        // Create the getters and setters for the property...
        Object.defineProperty(child.prototype, name, {
          // Getter proxies to Model#get()...
          get: function() { return this.get(name); },
          // Setter proxies to Model#set(attributes)
          set: function(value) {
            var data = {};
            data[name] = value;
            this.set(data);
          },
          // Make it configurable and enumerable so it's easy to override...
          configurable: true,
          enumerable: true
        });
        
      }
    });
  }

  // Return the new Model, now with getters and setters for each property!
  return child;
};