I'm creating a generic function that gets properties from an object using array.reduce. I would like the return type to only return the type of properties extracted from the original object

type Sample = {
  name: string;
  age: number;
  isAlive: boolean;
}

const sample: Sample = {
  name: "John Doe",
  age: 22,
  isAlive: true,
};

// What changes should I do here?
function getProps(...keys: (keyof Sample)[]) {
  return keys.reduce((acc, key) => {
    acc[key] = sample[key];

    return acc;
  }, {})
}

const result = getProps("name", "age");
/*
  I would like the result to have a type of:
  {
    name: string;
    age: number;
  }
*/

I saw this being done in zustand.js but I don't know how they did it. Any help is appreciated.

CodePudding user response：

Here's a quick solution. The key is using generics and the Pick utility type:

type Sample = {
  name: string;
  age: number;
  isAlive: boolean;
}

const sample: Sample = {
  name: "John Doe",
  age: 22,
  isAlive: true,
};

function getProps<K extends keyof Sample>(...keys: K[]): Pick<Sample, K> {
  return keys.reduce((acc, key) => {
    acc[key] = sample[key];
    return acc;
  }, {} as Pick<Sample, K>)
}

const result = getProps("name", "age");
// result has only name and age

Playground Link