a better way if iterating an object using lodash

Question

Using lodash I'm wondering if there is a better way of doing this.

I've got an array object like below.

    {
        "ALFA ROMEO": {
            "MITO": [{
                "carData": "stuff"
            }]
        },
        "AUDI": {
            "A1": [{
                    "carData": "stuff"
                },
                {
                    "carData": "stuff"
                }
            ],
            "Q3": [{
                "carData": "stuff"
            }],
            "A3": [{
                    "carData": "stuff"
                },
                {
                    "carData": "stuff"
                },
                {
                    "carData": "stuff"
                }
            ]
        }
    }

I'm using _.forEach to iterate through the object to structure the output simular to this:

    ALFA ROMEO - 1
        MITO (1)
    AUDI - 5
        A1 (2)
        Q3 (1)
        A3 (2)

Using this I can get part way there:

        _.forEach(jData, (val, key) => {
            console.log(key)
            _.forEach(val, (val, key) => {
                console.log('    ' + key + ' (' + val.length + ')')
            })
        })

Which give me this:

    ALFA ROMEO
        MITO (1)
    AUDI
        A1 (2)
        Q3 (1)
        A3 (2)

My question is this:

a) Is there a better way of doing this without a double loop?

b) Is the only way to get a total for each make by totalling up the model counts, or is there a better way of doing this?

Thanks.

As per my understanding, You will surely have to run through nested loops because the key values might change on run time. And the way to find the total count for each model of the car, it is in the format of the array, thus you can find out the length of the array and store them. — SARAN SURYA
– SARAN SURYA, Commented Mar 9, 2022 at 16:56

Barmar · Accepted Answer · 2022-03-09 17:21:14Z

2

There's no way to do it without nested looping, since you need to print each model.

You can use _.sumBy() to get the total lengths of the models, so you can show that before the loop.

const jData = {
  "ALFA ROMEO": {
    "MITO": [{
      "carData": "stuff"
    }]
  },
  "AUDI": {
    "A1": [{
        "carData": "stuff"
      },
      {
        "carData": "stuff"
      }
    ],
    "Q3": [{
      "carData": "stuff"
    }],
    "A3": [{
        "carData": "stuff"
      },
      {
        "carData": "stuff"
      },
      {
        "carData": "stuff"
      }
    ]
  }
};

_.forEach(jData, (val, key) => {
  let total = _.sumBy(_.toArray(val), 'length');
  console.log(`${key} - ${total}`)
  _.forEach(val, (val, key) => {
    console.log(`${key} (${val.length})`)
  })
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js"></script>

edited Mar 9, 2022 at 17:21

answered Mar 9, 2022 at 17:07

Barmar

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