Return new JS object using previous object values

user_16854409 0
Viewed 72

I have an object of objects (for example):

const previousMap = {123456: {title: 'Test 1', productID: 123456}, 234567: {title: 'Test 2', productID: 234567}}

and would like to return a new object, with each key as the titles of the previous object, and its values as the sku (which also happen to be the keys of the last object-- but I would rather use the .sku attribute).

For example:

const newMap = {'Test 1' : 123456, 'Test 2': 234567}

I have tried:

newMap = Object.entries(previousMap).map(([key, value]) => ({[value.title] : value.productID}))

but wind up getting an array of objects.

This is something that I feel as though I would normally be able to accomplish but my brain is really not working today. Any help = greatly appreciated :)

reactjs for-loop javascript
2 Answers

Another possible solution:
Changing the map to return an array of key and value [k,v] and then calling Object.fromEntries on it.

const previousMap = {
  123456: {
    title: 'Test 1',
    productID: 123456
  },
  234567: {
    title: 'Test 2',
    productID: 234567
  }
}

let newMap = Object.fromEntries(
  Object.entries(previousMap)
  .map(([key, value]) => [value.title, value.productID])
);

console.log(newMap)

user_135835100

A .map will, by definition, always return an array. Instead you can use .reduce, starting with an empty object as the initial value for your accumulator, and spread it into the new return object at each iteration:

const previousMap = {
  123456: {
    title: 'Test 1',
    productID: 123456
  },
  234567: {
    title: 'Test 2',
    productID: 234567
  }
}

const newMap = Object.entries(previousMap)
  .reduce(
    (acc, [key, value]) => ({
      ...acc,
      [value.title]: value.productID
    }), {}
  );

console.log(newMap);

You could also just accomplish this with a plain loop and keep mutating a single object instead, if you desired.

user_68313410
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