Facebook-Clone/frontend/reducers/comments_reducer.js

import {
  RECEIVE_COMMENTS,
  RECEIVE_COMMENT,
  REMOVE_COMMENT,
} from '../actions/comment_actions';
import merge from 'lodash/merge';

export default (state = {}, action) => {
  Object.freeze(state);
  let newState = merge({}, state);
  switch (action.type) {
    case RECEIVE_COMMENTS:
      return action.comments;
    case RECEIVE_COMMENT:
      newState[action.comment.id] = action.comment;
      return newState;
    case REMOVE_COMMENT:
      delete newState[action.commentId];
      return newState;
    default:
      return state;
  }
};