Retrieve a multitude of nested Records within the returnType that correlate with the number of arguments provided to the function

Question

Retrieve a multitude of nested Records within the returnType that correlate with the number of arguments provided to the function

My goal is to dynamically define a deeply nested ReturnType for a function based on the number of arguments passed in the "rest" parameter. For example, if we have:

getFormattedDates(
  dates: Date[],
  ...rest: string[] // ['AAA', 'BBB', 'CCC', etc...]
): Record<string, Record<string, Record<string,etc...>>>

The final nested object should be of type Record<string, Date[]>. In case there is no second argument, the return type should simply be Date[].

I have searched online for a solution but couldn't find a satisfactory answer that explains the logic behind it. This is my first time asking a question, so I hope I've provided enough clarity.

If anyone could provide insight into this issue, I would greatly appreciate it. Thank you!

typescript function typescript-typings return-type nested-object

Answer 1

Answer №1

You have the ability to create a recursive type by following this approach:

type ToRecord<T> = T extends [string, ...infer Rest]
    ? Record<string, ToRecord<Rest>>
    : Date[]

declare function getFormattedDates<T extends string[]>(
    dates: Date[],
    ...rest: T // ['AAA', 'BBB', 'CCC', etc...]
): ToRecord<T>

const p0 = getFormattedDates([]) // Date[]
const p1 = getFormattedDates([], 'AAA') // Record<string, Date[]>
const p3 = getFormattedDates([], 'AAA', 'BBB', 'CCC') // Record<string, Record<string, Record<string, Date[]>>>

Playground

Answer 2

You have the ability to create a recursive type by following this approach:

type ToRecord<T> = T extends [string, ...infer Rest]
    ? Record<string, ToRecord<Rest>>
    : Date[]

declare function getFormattedDates<T extends string[]>(
    dates: Date[],
    ...rest: T // ['AAA', 'BBB', 'CCC', etc...]
): ToRecord<T>

const p0 = getFormattedDates([]) // Date[]
const p1 = getFormattedDates([], 'AAA') // Record<string, Date[]>
const p3 = getFormattedDates([], 'AAA', 'BBB', 'CCC') // Record<string, Record<string, Record<string, Date[]>>>

Playground

Retrieve a multitude of nested Records within the returnType that correlate with the number of arguments provided to the function

Answer №1

Similar questions

When working with Typescript, NextAuth throws errors while embedding

What could be the reason for my npm package installed globally to not be able to utilize ts-node?

Check out the computed typescript types

use a map function that takes in two integers and apply it to a list containing multiple lists

Typedoc: only export contents from a particular file are documented

Having difficulty troubleshooting the /app router application on version 13.4.x

The JavaScript code is executing before the SPFX Web Part has finished loading on the SharePoint page

Using Typescript to retrieve the Return Type of a function when called with specific Parameter types

Is ngOnDestroy executed within Angular services?

Top method for changing Enum to Set in TypeScript

Error in ReactJS VSCode while integrating Cypress testing: The name 'cy' cannot be found

Allow for an optional second parameter in Typescript type definition

Utilizing References in React Components

Is there a way to change the data type of all parameters in a function to a specific type?

Transmit a form containing a downloaded file through an HTTP request

typescript add some flair to the setter function

Removing undefined elements from an array

Tips on preventing the copying of .txt and .xml files with the fs-extra.copySync function

Troubleshooting form submission issues in Angular 4

What is the correct way to define types for higher-order class components in TypeScript?