code: function (target, source, override) {
              //Use an empty object to avoid other bad JS code that modifies
              //Object.prototype.
              var empty = {}, prop;
              for (prop in source) {
                  if (override || !(prop in target)) {
                      target[prop] = source[prop];
                  }
              }
          }
docs: Simple function to mix in properties from source into target,
  but only if target does not already have a property of the same name.