Functional way to flatten nested array inside an object using lodash?

Question

I have this facebookResponseObject and i want to flatten the values which are of array type

Right now i'm using a reduce function like this but i was wondering if there's a more cleaner functional way to solve this...

Input Sample

const facebookResponseObject = {
  account_currency: "xxx",
  campaign_name: "xxxxxxxx",
  account_name: "xxxxxxxx",
  adset_name: "xxxxxxxx",
  ad_name: "xxxxxxxx",
  reach: "xxxx",
  impressions: "xxxx",
  frequency: "xxxx",
  spend: "xxxx",
  cpm: "xxxx",
  inline_link_clicks: "xxxx",
  cost_per_inline_link_click: "xxxx",
  inline_link_click_ctr: "xxxx",
  clicks: "xxxx",
  cost_per_unique_click: "xxxx",
  cost_per_action_type: [
    { action_type: "link_click", value: "xxxx" },
    { action_type: "landing_page_view", value: "xxxx" },
    { action_type: "post_engagement", value: "xxxx" },
    { action_type: "page_engagement", value: "xxxx" },
    { action_type: "lead", value: "xxxx" },
    { action_type: "video_view", value: "xxxx" },
    { action_type: "like", value: "xxxx" },
  ],
  actions: [
    { action_type: "link_click", value: "xxxx" },
    { action_type: "landing_page_view", value: "xxxx" },
    { action_type: "post_engagement", value: "xxxx" },
    { action_type: "page_engagement", value: "xxxx" },
    { action_type: "post_reaction", value: "xxxx" },
    { action_type: "lead", value: "xxxx" },
    { action_type: "post", value: "xxxx" },
    { action_type: "comment", value: "xxxx" },
    { action_type: "video_view", value: "xxxx" },
    { action_type: "like", value: "xxxx" },
  ],
  test_key: [
    { action_type: "test1", value: "xxxx" },
    { action_type: "test2", value: "xxxx" },
    { action_type: "test3", value: "xxxx" },
    { action_type: "test4", value: "xxxx" },
  ],
  cpc: "xxxx",
  ctr: "xxxx",
  date_start: "xxxx-xx-xx",
  date_stop: "xxxx-xx-xx",
  account_id: "xxxxxxxx",
};

Transform function

const formatResponse = _.reduce(
  facebookResponseObject,
  (acc, cur, key) => {
    if (_.isArray(cur)) {
      acc = {
        ...acc,
        ..._.chain(cur)
          .keyBy(obj => `${key}.${obj.action_type}`)
          .mapValues(v => v.value)
          .value(),
      };
    } else {
      acc[key] = cur;
    }
    return acc;
  },
  {},
);

Output

{
  account_currency: 'xxx',
  campaign_name: 'xxxxxxxx',
  account_name: 'xxxxxxxx',
  adset_name: 'xxxxxxxx',
  ad_name: 'xxxxxxxx',
  reach: 'xxxx',
  impressions: 'xxxx',
  frequency: 'xxxx',
  spend: 'xxxx',
  cpm: 'xxxx',
  inline_link_clicks: 'xxxx',
  cost_per_inline_link_click: 'xxxx',
  inline_link_click_ctr: 'xxxx',
  clicks: 'xxxx',
  cost_per_unique_click: 'xxxx',
  'cost_per_action_type.link_click': 'xxxx',
  'cost_per_action_type.landing_page_view': 'xxxx',
  'cost_per_action_type.post_engagement': 'xxxx',
  'cost_per_action_type.page_engagement': 'xxxx',
  'cost_per_action_type.lead': 'xxxx',
  'cost_per_action_type.video_view': 'xxxx',
  'cost_per_action_type.like': 'xxxx',
  'actions.link_click': 'xxxx',
  'actions.landing_page_view': 'xxxx',
  'actions.post_engagement': 'xxxx',
  'actions.page_engagement': 'xxxx',
  'actions.post_reaction': 'xxxx',
  'actions.lead': 'xxxx',
  'actions.post': 'xxxx',
  'actions.comment': 'xxxx',
  'actions.video_view': 'xxxx',
  'actions.like': 'xxxx',
  'test_key.test1': 'xxxx',
  'test_key.test2': 'xxxx',
  'test_key.test3': 'xxxx',
  'test_key.test4': 'xxxx',
  cpc: 'xxxx',
  ctr: 'xxxx',
  date_start: 'xxxx-xx-xx',
  date_stop: 'xxxx-xx-xx',
  account_id: 'xxxxxxxx'
}

user3297291 · Accepted Answer · 2021-10-26 11:09:25Z

You could use flatMap to iterate the object's entries.

Don't touch an entry that has a non-array value
When there is an array value, iterate over its elements to return new key-value pairs
- As a key, join the original key with the action_type
- As a value, take the value property
Because we're using flatMap, we ensure we're not returning a nested list.
Use Object.fromEntries to transform back in to an object

const flatEntries = (obj) => Object
  .entries(obj)
  .flatMap(
    ([ k, v ]) => Array.isArray(v)
      ? v.map(a => [ `${k}.${a.action_type}`, a.value ] )
      : [[k, v]]
  );

const flattenObject = obj => Object.fromEntries(flatEntries(obj));
  
console.log(flattenObject(facebookResponseObject()));


function facebookResponseObject() { return {
  account_currency: "xxx",
  campaign_name: "xxxxxxxx",
  account_name: "xxxxxxxx",
  adset_name: "xxxxxxxx",
  ad_name: "xxxxxxxx",
  reach: "xxxx",
  impressions: "xxxx",
  frequency: "xxxx",
  spend: "xxxx",
  cpm: "xxxx",
  inline_link_clicks: "xxxx",
  cost_per_inline_link_click: "xxxx",
  inline_link_click_ctr: "xxxx",
  clicks: "xxxx",
  cost_per_unique_click: "xxxx",
  cost_per_action_type: [
    { action_type: "link_click", value: "xxxx" },
    { action_type: "landing_page_view", value: "xxxx" },
    { action_type: "post_engagement", value: "xxxx" },
    { action_type: "page_engagement", value: "xxxx" },
    { action_type: "lead", value: "xxxx" },
    { action_type: "video_view", value: "xxxx" },
    { action_type: "like", value: "xxxx" },
  ],
  actions: [
    { action_type: "link_click", value: "xxxx" },
    { action_type: "landing_page_view", value: "xxxx" },
    { action_type: "post_engagement", value: "xxxx" },
    { action_type: "page_engagement", value: "xxxx" },
    { action_type: "post_reaction", value: "xxxx" },
    { action_type: "lead", value: "xxxx" },
    { action_type: "post", value: "xxxx" },
    { action_type: "comment", value: "xxxx" },
    { action_type: "video_view", value: "xxxx" },
    { action_type: "like", value: "xxxx" },
  ],
  test_key: [
    { action_type: "test1", value: "xxxx" },
    { action_type: "test2", value: "xxxx" },
    { action_type: "test3", value: "xxxx" },
    { action_type: "test4", value: "xxxx" },
  ],
  cpc: "xxxx",
  ctr: "xxxx",
  date_start: "xxxx-xx-xx",
  date_stop: "xxxx-xx-xx",
  account_id: "xxxxxxxx",
}; }

xqcccccccccc · Accepted Answer · 2021-10-26 11:34:54Z

1

Thanks for the help @user3297291, i'm gonna use a slightly modified version to your answer (using lodash)

const formatResponse = obj =>
  _.chain(obj)
    .toPairs()
    .flatMap(([key, value]) =>
      _.isArray(value)
        ? _.map(value, actionObj => [`${key}.${actionObj.action_type}`, actionObj.value])
        : [[key, value]],
    )
    .fromPairs()
    .value();

answered Oct 26, 2021 at 11:34

xqcccccccccc

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