How to add to an array within an object

Question

I have this object and I'm trying to convert it.

names = {
  animals: ['Dog', 'Cat', 'Snake'],
  flowers: ['Rose', 'Daisy']
}

I want to convert it into something like this

newObject = {
  type: ['animals', 'flowers']
  subtype: ['Dog', 'Cat', 'Snake', 'Rose', 'Daisy']
}

I wrote the following function but for some reason it's not populating correctly.

const newObject = {};

Object.keys(names).map(type => {
  newObject['types'] = [...newObject['types'], type];
      names[type].map(subtype => {
        newObject['subtypes'] = [...newObject['subtypes'], subtype];
      })
    })

Nick Parsons · Accepted Answer · 2020-07-06 11:18:25Z

5

Your .map() callback should return what you want each element to turn into, so the callback behaves somewhat like a transformation function. However, for a case like this, you don't need to use .map() and can just extract the keys and values from the object. As your values are arrays, you can use .flat() to merge the array of arrays into the one larger array of values for your subtype key:

const names = {
  animals: ['Dog', 'Cat', 'Snake'],
  flowers: ['Rose', 'Daisy']
}

const type = Object.keys(names);
const subtype = Object.values(names).flat();

const newObject = {type, subtype};
console.log(newObject);

edited Jul 6, 2020 at 11:18

answered Jul 6, 2020 at 10:18

Nick Parsons

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Comments

Edoardo Pacciani · Accepted Answer · 2020-07-06 10:18:18Z

0

newObject = {
  type: ['animals', 'flowers']
  subtype: [...names.animals, ...names.flowers] 
}

answered Jul 6, 2020 at 10:18

Edoardo Pacciani

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1 Comment

Tushar Over a year ago

This implementation is not very flexible as you have to hard code values.

blex · Accepted Answer · 2020-07-06 10:21:00Z

0

You can also use reduce to build a new object:

const names = {
  animals: ['Dog', 'Cat', 'Snake'],
  flowers: ['Rose', 'Daisy']
};

const res = Object.entries(names)
                  .reduce(
                    ({type, subtype}, [key, values]) => ({
                      type: type.concat(key),
                      subtype: subtype.concat(values)
                    }),
                    { type: [], subtype: [] } // Starting value
                  );

console.log(res);

answered Jul 6, 2020 at 10:21

blex

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Comments

Omer · Accepted Answer · 2020-07-06 10:26:03Z

0

Global solution for any keys and values

use Object.keys and Object.values with array.reduce() :)

const names = {
   animals: ['Dog', 'Cat', 'Snake'],
   flowers: ['Rose', 'Daisy']
}

const newObject = {
   type: Object.keys(names),
   subtype: Object.values(names).reduce((acc, item)=> [...acc, ...item],[])
}

console.log(newObject);

answered Jul 6, 2020 at 10:26

Omer

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