How to get the array object type in typescript

Question

For example I have an array data

const Arr = [
  {
    name: 'setTitle',
    method: (title: string) => {
      return title;
    }
  },
  {
    name: 'getName',
    method: () => {
      return 'hello world';
    }
  }
];

I want get type like this

type Result = {
  setTitle: (title: string) => string;
  getName: () => string
}

How to derive it directly from typescript?

Does this answer your question? Typescript: Retrieve element type information from array type — Nick Bailey
– Nick Bailey, Commented Jul 17, 2022 at 3:34

Tobias S. · Accepted Answer · 2022-07-17 22:11:19Z

1

You would have to use as const when declaring Arr to preserve the narrowed type information of the name properties.

const Arr = [
  {
    name: 'setTitle',
    method: (title: string) => {
      return title;
    }
  },
  {
    name: 'getName',
    method: () => {
      return 'hello world';
    }
  }
] as const;

Now the Result type can be constructed like this:

type Arr = typeof Arr

type Result = {
  -readonly [K in Arr[number] as K["name"]]: K["method"]
}

// type Result = {
//     setTitle: (title: string) => string;
//     getName: () => string;
// }

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answered Jul 17, 2022 at 22:11

Tobias S.

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