converting an array into object in typescript

Question

I have an array of objects:

const users: Person[] = [{name: 'Erich', age: 19}, {name: 'Johanna', age: 34}, {name: 'John', age: 14}];

Where

interface Person {
    age: number;
    name: string;
};

I need to convert it to the type NFCollection which looks so:

interface NFCollection {
    type: string;
    data: Person[];
}

The result should looks like this:

const nfCollection: NFCollection = {
    type: 'adults',
    data: [{name: 'Erich', age: 19}, {name: 'Johanna', age: 34}]
}

where the data includes only those persons whose age >= 18.

So I could start writing something like:

const nfCollection: NFCollection = users.filter(u => u.age >= 18); // something else should follow the chain?

but then I would like to convert it to the NFCollection type. How would I do that? Preferably in a memory efficient way, cos the array could be relatively big.

const myNFCollection = { type: "adults", data: nfCollection };...? — k.tten
– k.tten, Commented Nov 1, 2022 at 1:52
Yes, that's how I actually implemented it, but I thought I could easily do this in place, like within the same chain of functions. — Alex
– Alex, Commented Nov 1, 2022 at 2:02

CertainPerformance · Accepted Answer · 2022-11-01 01:52:40Z

1

Just put the filtered array as a property of a new object?

const nfCollection = {
    type: 'adults',
    data: users.filter(u => u.age >= 18)
};

Then nfCollection will have the same type as your NFCollection interface.

answered Nov 1, 2022 at 1:52

CertainPerformance

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3 Comments

Alex Over a year ago

Yes, that's how I actually implemented it, but I thought I could easily do this in place, like within the same chain of functions.

CertainPerformance Over a year ago

A plain object literal definition is pretty easy to do in one place..? I suppose you could chain off of the .filter to construct the surrounding object (via .reduce), but it would look really really weird and wouldn't make sense users.filter(u => u.age >= 18).reduce((_, __, ___, data) => ({ type: 'adults', data })) plus tedious initial value typing

Alex Over a year ago

Yes, I agree, it looks weird. I will go with the proposed solution then. Thank you!

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