Advertisements How to create a generic type that resolves to the type of a nested property Say I have a configuration type type Config = { parent: { child: boolean } } I would like something similar to type ChildConfigType = NestedType<Config, ‘parent.child’> // boolean type ParentConfigType = NestedType<Config, ‘parent’> // {child: boolean} I have… Read More How to implement a TypeScript generic type for nested properties that resolves to their types?

Advertisements I want to make a function that receives string | undefined and also returns string | undefined. This was my first approach: sanitizeName: (name: string | undefined): string | undefined => { return name?.replace(…) }, However, when I call this function with a string argument, I know for sure it will also return a… Read More How to solve this TypeScript Generics error?

Advertisements Essentially, what I am trying to write is a function that accepts an array of different types, (do something with that), and then return a type based on only the last element in that array (previous elements have been processed, but only the last element is used for the return value). I know I… Read More Extract type of last element of tuple in TypeScript

Advertisements I’d like to constrain a function such that it accept an object as an argument, and returns an object of the exact same shape. That object’s keys can be any string, and I’d like to tell typescript that the return object has the same keys. I.e. interface ConstrainedObject { [key: string]: string[]; } function… Read More Function that returns the same object shape as it accepted in typescript

Advertisements Suppose I have an interface in typescript as follows: interface I1 { name: string, age: number } And I have another interface that accesses interface properties: interface I2<T> { getValue: (arg0: keyof T) => any } I want to be able to pass in another interface into I2 such that you can only pass… Read More How can I index a generic with an with the argument passed in to function in Typescript

Advertisements How can I create an optional function argument who’s type is generic? I have the following type definition: type Ok<T> = { ok: true; value: T } I want to write a function that combines the behavior of the two following functions into one: const Ok = <T>(value: T): Ok<T> => { return {… Read More Generic, optional type as an optional argument in TypeScript

Advertisements type StringTyped = {[key: string]: any}; type ShouldBeStringType = keyof StringTyped; const test:ShouldBeStringType = 2; // but this is allowed? I am trying to have a generic Type that relies on keyof actually returning the type which is specified, but keyof seems to always return the type string | number, even if I specify… Read More Typescript typing with keyof always has ambigious typing, even when specified

Advertisements I would like to create a function A, which returns function B, where the valid inputs to function B depend on the inputs to function A. The code below attempts to achieve this, but the linter expects the input for the second function to only ever be "a". I’d like valid inputs to be… Read More How can this nested function interface be achieved?

Advertisements I have a class called Entity like so: class Entity { constructor(readonly someValue: string) {} someFunction() {} } Now I want to create a class which manages these entities, being able to create instances of them. Since I might potentially derive those entities, the entity class to be used should be a generic class… Read More Is it possible to create an instance from a generic type?

Advertisements How to return the same type of the parameter if passed to the function, else fallback to another required parameter? const r = <Name extends string, R extends string>({ name, resource }: { name?: Name, resource: R }) => { return { // here the type of the "name" should be same as the… Read More Typescript function return type of the optional property as const with default