function mergePropsStack(
  propsStack: Array<Object>,
  defaultValues: Object
): Object {
  return propsStack.reduce((prev, cur) => {
    for (const prop in cur) {
      if (cur[prop] != null) {
        prev[prop] = cur[prop];
      }
    }
    return prev;
  }, Object.assign({}, defaultValues));
}
Merges the prop stack with the default values.