Underscore/Lodash: Group object by substring of key

Question

I am attempting to Group a object into a more organised structure based on a substring of the object key.

Below is a example of the object that I am passing:

var data = {
  "summ_example_1": {
    "value": 40464.284237
  },
  "summ_example_number_2": {
    "value": 39260.605837
  },
  "in_process_example_1": {
    "count": 10,
    "value": 10
  },
  "in_process_example_2": {
    "count": 12,
    "value": 12.5
  },
  "in_process_example_3": {
    "count": 0,
    "value": 0
  },
  "awaiting_example_1": {
    "count": 17,
  },
  "awaiting_example_2": {
    "count": 51,
  }
}

The output that I am wanting is:

{ summ:
    ["summ_example_1": {"value": 40464.284237},
     "summ_example_number_2": {"value": 39260.605837}],
  in:
    ["in_process_example_1": {"count": 10, "value": 10},
     "in_process_example_2": {"count": 12, "value": 12.5},
     "in_process_example_3": {"count": 0, "value": 0}],
  awaiting:
    ["awaiting_example_1": {"count": 17},
     "awaiting_example_2": {"count": 51"}]}

I have attempted grouping the object using groupBy within both Lodash and Underscore.js without any luck.

Inside underscore I can use the following code (Note that this does not work in Lodash as I can not seem to get the value of the Object Key:

var grouped = _.groupBy(data, function(val, key){
    return key.substr(0, key.indexOf('_'));
});

which produces the following output:

{ summ:
    [{"value": 40464.284237},
     {"value": 39260.605837}],
  in:
    [{"count": 10, "value": 10},
     {"count": 12, "value": 12.5},
     {"count": 0, "value": 0}],
  awaiting:
    [{"count": 17},
     {"count": 51"}]}

However I want to keep the Object Keys inside my output and as you can see it is removing them.

Is what I am doing possible?

Apologies if this doesn't make sense or has already been asked, but I have been searching for a solution for more time than I would have liked and am starting to run out of ideas.

Thank you for taking the time to read this and please feel free to ask any questions!

Answer 1

You could take the entries of the object and build a new key and group by this key.

 var data = { summ_example_1: { value: 40464.284237 }, summ_example_number_2: { value: 39260.605837 }, in_process_example_1: { count: 10, value: 10 }, in_process_example_2: { count: 12, value: 12.5 }, in_process_example_3: { count: 0, value: 0 }, awaiting_example_1: { count: 17 }, awaiting_example_2: { count: 51 } }, result = Object.entries(data).reduce((r, [k, v]) => { var key = k.replace(/_.*$/, '') ; (r[key] = r[key] || {})[k] = v; return r; }, {}); console.log(result); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

Answer 2

Lodash's _.groupBy() calls the iteratee with the only the value, in addition the result of groupBy is an object of arrays, not an object of objects like you need.

Solution 1 - lodash:

You can create a function with _.flow() that maps each object to include the group key ( summ for example), and them merge them together:

 const { flow, map, partialRight: pr, spread, merge } = _ const fn = flow( pr(map, (v, k) => ({ [k.split('_')[0]]: { [k]: v }})), // format each object to have the group key - summ for example spread(merge) // merge all objects together ) const data = { summ_example_1: { value: 40464.284237 }, summ_example_number_2: { value: 39260.605837 }, in_process_example_1: { count: 10, value: 10 }, in_process_example_2: { count: 12, value: 12.5 }, in_process_example_3: { count: 0, value: 0 }, awaiting_example_1: { count: 17 }, awaiting_example_2: { count: 51 } }; const result = fn(data); console.log(result); 

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 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.js"></script> 

Solution 2 - lodash/fp

Since lodash/fp _.map() doesn't pass the key to the iteratee, use _.pairs() to create a [key, value] tuple. Map the tuples to include the group key, and merge them all together.

 const { flow, toPairs, map, mergeAll } = _ const fn = flow( toPairs, map(([k, v]) => ({ [k.split('_')[0]]: { [k]: v }})), mergeAll ) const data = { summ_example_1: { value: 40464.284237 }, summ_example_number_2: { value: 39260.605837 }, in_process_example_1: { count: 10, value: 10 }, in_process_example_2: { count: 12, value: 12.5 }, in_process_example_3: { count: 0, value: 0 }, awaiting_example_1: { count: 17 }, awaiting_example_2: { count: 51 } }; const result = fn(data); console.log(result); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

 <script src='https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)'></script>