Getting the length of a many nested objects with dynamic keys in an array

Question

I'm trying to get the length of many nested objects with dynamic keys in an array as the below:

Input:

{
  "a": {
    "deptAS": [
      {...}
    ],
    "deptDr": [
      {...},
      {...},
      {...},
      {...},
      {...},
      {...}
    ],
    "deptES": [
      {...},
      {...}
    ],
    "deptGW": [
      {...
      }
    ]
  },
  "b": {
    "deptDr": [
      {...},
      {...},
      {...},
      {...},
      {...}
    ],
    "deptES": [
      {...},
      {...},
      {...},
      {...}
    ],
    "deptLU": [
      {...},
      {...}
    ],
    "deptSR": [
      {...},
      {...}
    ]
  },
}

Which would return:

"a": {
  "deptAS": 1,
  "deptDr": 6
  "deptES": 2,
  "deptGW": 1
}
"b": {
  "deptDr":5,
  "deptES":4,
  "deptLU":2,
  "deptSR":2,
}

I've tried various .map and lodash functions but can't get the data out in the format required, but I suspect the solution is very simple.

There is access to Lodash in the project already so that can be used

Nina Scholz · Accepted Answer · 2022-11-23 13:02:36Z

2

You could take a recursive approach and check if the value is an array or not.

const
    data = { a: { deptAS: [{}], deptDr: [{}, {}, {}, {}, {}, {}], deptES: [{}, {}], deptGW: [{}] }, b: { deptDr: [{}, {}, {}, {}, {}], deptES: [{}, {}, {}, {}], deptLU: [{}, {}], deptSR: [{}, {}] } },
    getLength = object => Object.fromEntries(Object
        .entries(object)
        .map(([k, v]) => [k, v.length ?? getLength(v)])
    ),
    result = getLength(data);

console.log(result);

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

edited Nov 23, 2022 at 13:02

answered Nov 23, 2022 at 12:52

Nina Scholz

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Comments

gog · Accepted Answer · 2022-11-23 13:28:43Z

1

With lodash, it's literally a one-liner:

result = _.mapValues(yourObject, v => _.mapValues(v, 'length'))

docs: _.mapValues

edited Nov 23, 2022 at 13:28

answered Nov 23, 2022 at 13:22

gog

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Comments

Erique Bomfim · Accepted Answer · 2022-11-23 13:22:20Z

p = {
  "a": {
    "deptAS": [
      {}
    ],
    "deptDr": [
      {},
      {},
      {},
      {},
      {},
      {}
    ],
    "deptES": [
      {},
      {}
    ],
    "deptGW": [
      {
      }
    ]
  },
  "b": {
    "deptDr": [
      {},
      {},
      {},
      {},
      {}
    ],
    "deptES": [
      {},
      {},
      {},
      {}
    ],
    "deptLU": [
      {},
      {}
    ],
    "deptSR": [
      {},
      {}
    ]
  }
}

calcProp = function(obj){
  
    const _props = Object.keys(obj);
    var _output = {};

    _props.forEach(_p=>{
      /* this way we avoid string calculation*/
      if (obj[_p].constructor.name == "Array"){
          _output[_p] = obj[_p].length
      }
      /* this way we go thought any level*/
      if (obj[_p].constructor.name == "Object"){
          _output[_p] = calcProp(obj[_p])
      }
    })

    return _output;
}
  
d = calcProp(p);
      
console.log(d);

Majed Badawi · Accepted Answer · 2022-11-23 14:28:53Z

0

Using Object#entries and Array#reduce, iterate over the object's pairs
For every pair, add a new entry with the key and the value as the object with counts

const obj = {
  "a": {
    "deptAS": [ {} ],
    "deptDr": [ {}, {}, {}, {}, {}, {} ],
    "deptES": [ {}, {} ],
    "deptGW": [ {} ]
  },
  "b": {
    "deptDr": [ {}, {}, {}, {}, {} ],
    "deptES": [ {}, {}, {}, {} ],
    "deptLU": [ {}, {} ],
    "deptSR": [ {}, {} ]
  }
};

const res = Object.entries(obj).reduce((acc, [key, value]) => {
  acc[key] = {};
  Object.entries(value).forEach(([prop, arr]) => { acc[key][prop] = arr.length });
  return acc;
}, {});

console.log(res);

edited Nov 23, 2022 at 14:28

answered Nov 23, 2022 at 12:53

Majed Badawi

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3 Comments

gog Over a year ago

for the given example, this will create 10 intermediate objects which serve no obvious purpose.

Majed Badawi Over a year ago

@gog why 10? what do you suggest other than modifying the main object reference?

gog Over a year ago

when using reduce, modify the accumulator object directly instead of creating a new object each time.

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