export const commentList = (state, action) => {
  switch (action.type) {
    case 'ADD_COMMENT':
      let newComment = { comment: action.data, id: +new Date };
      return state.concat([newComment]);
    case 'DELETE_COMMENT':
      let commentId = action.data;

    default:
      return state || [];
  }
}

case 'DELETE_COMMENT':
  const commentId = action.data;
  return state.filter(comment => comment.id !== commentId);

case 'DELETE_COMMENT':
  return state.filter(({ id }) => id !== action.data);