Is it now possible to create a typed zip function using Typescript 3.0's generic rest parameters?

Consider the ability to define a zip function with TypeScript that can accept a variable number of parameters:

function genericZip<T extends Array<any>>(...args: T[]): T[][]

Could it be possible to create a zip function with rest parameters and a generic return type?

function zip(...args) {
    return args[0].map((_, index) => args.map(row => row[index]));
}

It seems that even with the introduction of new generic rest parameters in Typescript 3.0, such as <T extends any[]>, they are still insufficient to fully type this particular function.

typescript

Answer №1

When working with TypeScript 3.1 and utilizing mapped tuples, you can achieve the following:

type Zip<T extends unknown[][]> = { [I in keyof T]: T[I] extends (infer U)[] ? U : never }[];
function zip<T extends unknown[][]>(...args: T): Zip<T> {
    return <Zip<T>><unknown>(args[0].map((_, c) => args.map(row => row[c])));
}

declare const y: number[], z: string[]; 
let yz = zip(y, z);  // [number, string][]

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