Convert array of object with different key into one object

Question

I have an object like below.

{
  A: { lists: 2, list: [ [Object], [Object] ] },
  B: { lists: 2, list: [ [Object], [Object] ] },
  C: { lists: 1, list: [ [Object]] }
}

After I do a map on an object list result, like below

 const list = Object.entries(result).map(([k, v]) => ({[k]: v.lists}));

the result I am getting is

[{"A":2},{"B":2},{"C":1}]

But what I actually want is

{A: 2, B: 2, C: 1}

How can I achieve that?

Does this answer your question? Reversing an Object.entries conversion — Emile Bergeron
– Emile Bergeron, Commented Nov 10, 2020 at 14:01

Derek Wang · Accepted Answer · 2020-11-10 13:58:36Z

8

You can use Array.prototype.reduce as follows.

const list = Object.entries(result).reduce((acc, [k, v]) => {
  acc[k] = v.lists;
  return acc;
}, {});

answered Nov 10, 2020 at 13:58

Derek Wang

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Comments

Ori Drori · Accepted Answer · 2020-11-10 14:01:12Z

When you map the entries change them to [k, v.lists], and then convert to an object using Object.fromEntries():

const result = { A: { lists: 2 }, B: { lists: 2 }, C: { lists: 1 }};

const list = Object.fromEntries(Object.entries(result).map(([k, v]) => [k, v.lists]));

console.log(list);

With lodash you can use _.mapValues() to use lists as the values of the properties:

const result = { A: { lists: 2 }, B: { lists: 2 }, C: { lists: 1 }};

const list = _.mapValues(result, 'lists');

console.log(list);

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