Combine values from an object within an object Javascript

Question

I am trying to combine ids for an object. The original object looks like this:

{
   "Car1":{
      "139":{
         "count":3,
         "ids":[
            "336",
            "347",
            "453"
         ]
      },
      "140":{
         "count":1,
         "ids":[
            "338"
         ]
      }
   },
   "Car2":{
      "157":{
         "count":1,
         "ids":[
            "4449"
         ]
      }
   }
}

I am trying to combine the ids for each "car" so that it looks like this.

{
   "Car1":{
      "ids":[
         "336",
         "347",
         "453",
         "338"
      ]
   },
   "Car2":{
      "ids":[
         "4449"
      ]
   }
}

Basically just trying to create a function that reduces the unneeded information and combines the ids

Answer 1

You may use the Array.reduce

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce

Object.entries(data)
  .reduce((acc, [carName, carData]) => {
    acc[carName] = { ids: Object.values(carData).flatMap(({ids}) => ids) };
    return acc;
  },{});

I further commented each line in the demo:

const data = {
   "Car1":{
      "139":{"count":3,"ids":["336","347","453"]},
      "140":{"count":1, "ids":["338"]}
   },
   "Car2":{
      "157":{"count":1,"ids":["4449"]}
   }
};

const transformedData =
//for all property name=>value pairs in data
Object.entries(data)
  //return the reduced version...
  //for each couple as carName=>carData
  .reduce((acc, [carName, carData]) => {
    //sets the property carName in the accumulator
    acc[carName] = {
      //where the id property is the merge of all the ids found in the whole list
      ids: Object.values(carData).flatMap(({ids}) => ids)
    };
    return acc;
  },
  //inits the accumulator with empty object
  {});

console.log(transformedData);