javascript: initialize an object with nested properties

gistfile1

var app = {}

app.ensure_struct = function(atts,scope){
  var scope = scope || this;
  if (atts == "") {
      return scope;
  }
  var parts = atts.split('.'),
      first_attribute = parts.shift();

  if (typeof (scope[first_attribute]) === 'undefined') {
      scope[first_attribute] = {};
  }
  app.ensure_struct(parts.join('.'), scope[first_attribute]);
  return scope;
}