I have array. I want to create an object with properties of the array with specific type for each of them.

export interface SomeNumbers {
  name: string;
  value: number;
}
const arr = ['first', 'second', 'third'];

const objectOfValues = {}; // HOW TO SET A TYPE HERE?

arr.forEach((val, index) => {
  objectOfValues[val]= {
    name: val,
    value: index
  };
});

CodePudding user response：

I think you are trying to do something like this:

    export interface SomeNumbers {
      name: string;
      value: number;
    }

    const arr = ['first', 'second', 'third'];

    const objectOfValues: { [key: string]: SomeNumbers }  = {};

    arr.forEach((val, index) => {
      objectOfValues[val] = {
        name: val,
        value: index
      };
    });

CodePudding user response：

You can use reducer pattern for both type and runtime scopes.

export interface SomeNumbers<N, V> {
    name: N;
    value: V;
}

type Reducer<
    Tuple extends Array<any>,
    Acc extends Record<string, any> = {},
    Index extends number[] = []
    > =
    Tuple extends []
    ? Acc
    : (Tuple extends [infer Head, ...infer Tail]
        ? (Head extends PropertyKey
            ? Reducer<
                Tail,
                Acc & Record<Head, SomeNumbers<Head, Index['length']>>,
                [...Index, 1]
            >
            : never)
        : never)



const builder = <Tuple extends string[]>(tuple: [...Tuple]) =>
    tuple.reduce((acc, elem, index) => ({
        ...acc,
        [elem]: {
            name: elem,
            value: index
        }
    }), {} as Reducer<Tuple>)

const result = builder(['first', 'second', 'third'])

//  {
//     name: "first";
//     value: 0;
// }
result.first 

Playground

Reducer type does exactly the same job as builder function. Except Reducer iterates recursively through the tuple.

Reducer - iterates recursively through the Tuple and intersects Acc with SomeNumbers<N,V>. Index - is extra tuple for indexing. Every time I increasing Index tuple for 1 element. It just coresponds to the index of iterated element

You can find more examples in my blog