How can I pass an attribute as a parameter with Typescript?

Question

I am a newbie with Angular 8.
I would like to pass an array of interfaces to a sort function, and I would like to pass interface attributes as parameters.
For now I have tried this way:

sortBy<T, K keyof T>(field: K, arr: T[], mode: 'Asc' | 'Desc'): T[] {
    const res = arr.sort((x, y) => x[field].localCompare(y[field], undefined, { sesitivity: 'base' }));

    return mode === 'Asc'
      ? res
      : res.reverse();
}

But I am noticing that the editor (VSCode) is reporting to me some inaccuracies, in particular:

I can't decipher these comments. What should I do to optimize my function?

JB Nizet · Accepted Answer · 2020-01-20 10:39:15Z

1

You don't need the K parameter:

sortBy<T>(field: keyOf T, arr: T[], mode: 'Asc' | 'Desc'): T[]

answered Jan 20, 2020 at 10:39

JB Nizet

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1 Comment

Memmo Over a year ago

Now Property 'localCompare' does not exist on type 'T[keyof T]' and don't compile. While the rest is ok.

Soukyone · Accepted Answer · 2020-01-20 10:40:19Z

1

In your case, field is typed as an object k, and ofc, you cannot use an object as index. If you wanna call a parameter, you have 2 options :

const x = object.param;

Or

const x = object['param'];

In your case, your param 'field' need to be a string, then you will be able to do:

x[field]

answered Jan 20, 2020 at 10:40

Soukyone

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3 Comments

Memmo Over a year ago

No error on VSCode, but an error in the console ERROR TypeError: x[field].localCompare is not a function, that compromises the functioning of the sorting.

Soukyone Over a year ago

It means, your x[field] object, doesn t have a function localCompare, you tried to console.log the variable ?

Memmo Over a year ago

My fault, I forgot an e :)

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