How to create an object with some array values without saving reference to the array?

Question

In other words; how can I convert

// an array of length >= 3
let myArray = returnOfSomeParametricFunction(); // assuming repeating rhs removes dryness

let myObj = { staticKeyName: myArray[1], anotherStaticKeyName: myArray[2] };

to a single liner. Perhaps something like:

let myObj = returnOfSomeParametricFunction().reduce(arr=> { staticKeyName: arr[1], anotherStaticKeyName: arr[2] };

Like `(a => ({ staticKeyName: a[1], anotherStaticKeyName: a[2] }))(returnOfSomeParametricFunction())`? — jcalz, May 06 '20 at 17:03
From the above, `const [,staticKeyName,anotherStaticKeyName] = returnOfSomeParametricFunction();` — Heretic Monkey, May 06 '20 at 17:07
@HereticMonkey But they're not trying to make variables named `staticKeyName` and `anotherStaticKeyName`. Those are intended to be property names — jcalz, May 06 '20 at 17:12
So more like [Destructure array to object property keys](https://stackoverflow.com/q/38242744/215552) then? — Heretic Monkey, May 06 '20 at 17:14
Yeah, it's a duplicate of that one. Surprised not to see the arrow function solution in there though. — jcalz, May 06 '20 at 17:15
Ah, the other one doesn't have the constraint that the array not be a named variable. I guess it's not quite a duplicate. — jcalz, May 06 '20 at 17:18

score 1 · Accepted Answer · answered May 06 '20 at 17:15

In this case, if I needed to do it in one line and not introduce a new variable in the same scope as myObj, and I didn't care about readability, I'd use an arrow function like this:

let myObj = (a => ({ staticKeyName: a[1], anotherStaticKeyName: a[2] }))(
  returnOfSomeParametricFunction());

You can verify that myObj has the properties of the right types. For example, given

declare function returnOfSomeParametricFunction(): [Date, number, string];

Then myObj would have type:

/*
let myObj: {
    staticKeyName: number;
    anotherStaticKeyName: string;
}
*/

Okay, hope that helps; good luck!

Playground link to code

How to create an object with some array values without saving reference to the array?

1 Answers1