Support nested id's for backbone.js Model

gistfile1.js

(function(Backbone){
  // Helper function to accessing nested JavaScript objects with string key
// via. http://stackoverflow.com/a/6491621
  var byString = function(object, stringKey) {
    stringKey = stringKey.replace(/\[(\w+)\]/g, '.$1'); // convert indexes to properties
    stringKey = stringKey.replace(/^\./, '');           // strip a leading dot
    var a = stringKey.split('.');
    while (a.length) {
      var n = a.shift();
      if (n in object) {
        object = object[n];
      } else {
        return;
      }
    }
    return object;
  };

// Helper function to test the existence of multiple levels
// via. http://stackoverflow.com/a/2631198
  var checkNested = function(obj, args) {
    for (var i = 0; i < args.length; i++) {
      if (!obj.hasOwnProperty(args[i])) {
        return false;
      }
      obj = obj[args[i]];
    }
    return true;
  };

  ModelNestedID = Backbone.Model.extend({
    set: function(key, value, options) {
      var attrs, attr, val;

      // Handle both `"key", value` and `{key: value}` -style arguments.
      if (_.isObject(key) || key == null) {
        attrs = key;
        options = value;
      } else {
        attrs = {};
        attrs[key] = value;
      }

      // Extract attributes and options.
      options || (options = {});
      if (!attrs) return this;
      if (attrs instanceof Backbone.Model) attrs = attrs.attributes;
      if (options.unset) for (attr in attrs) attrs[attr] = void 0;

      // Run validation.
      if (!this._validate(attrs, options)) return false;

      // Check for changes of `id`.
      if (checkNested(attrs, this.idAttribute.split('.'))) this.id = byString(attrs, this.idAttribute);

      var changes = options.changes = {};
      var now = this.attributes;
      var escaped = this._escapedAttributes;
      var prev = this._previousAttributes || {};

      // For each `set` attribute...
      for (attr in attrs) {
        val = attrs[attr];

        // If the new and current value differ, record the change.
        if (!_.isEqual(now[attr], val) || (options.unset && _.has(now, attr))) {
          delete escaped[attr];
          (options.silent ? this._silent : changes)[attr] = true;
        }

        // Update or delete the current value.
        options.unset ? delete now[attr] : now[attr] = val;

        // If the new and previous value differ, record the change.  If not,
        // then remove changes for this attribute.
        if (!_.isEqual(prev[attr], val) || (_.has(now, attr) != _.has(prev, attr))) {
          this.changed[attr] = val;
          if (!options.silent) this._pending[attr] = true;
        } else {
          delete this.changed[attr];
          delete this._pending[attr];
        }
      }

      // Fire the `"change"` events.
      if (!options.silent) this.change(options);
      return this;
    }
  });

  Backbone.Model = ModelNestedID;

})(Backbone);