Questions tagged [typescript-generics]
For questions related specifically to usage of generic types in TypeScript.
typescript-generics
4,709
questions
1
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0
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8
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TS doesn't match exact type to generic? [duplicate]
type Input = 'a' | 'b';
type ResultOf<T extends Input> = T extends 'a' ? 'A' : 'B';
function foo<T extends Input>(input: T): ResultOf<T> {
return input === 'a' ? 'A' : 'B';
}
...
0
votes
0
answers
13
views
Constraining a generic parameter to be a record with a single key in Typescript
I would like to constrain the a generic parameter T of a class MyClass<T> such that T is valid for any record which has only 1 key:
type ValidShape = {
key: any;
};
type InvalidShape = {
...
- 1
1
vote
1
answer
27
views
Function input conditional object keys based on value of other keys
I would like to have a function whose input object keys are statically typed depending on the given value of some key. Here is a TypeScript playground with a failing test:
Playground Link
export type ...
- 796
0
votes
1
answer
24
views
How do i write recursive Routes type with absolute paths?
I have react-router v6 in my app, and i want all paths in router config object to be absolute
But i need to ensure that path of child route of any depth begins with its parent path, otherwise app just ...
- 49
0
votes
1
answer
40
views
Infer the return type based on a parameter
I've a function that takes an action "DELETE"|"RENAME"|"MOVE"|etc...
I would like the return type to be different depending on the action fired.
For example, "DELETE&...
- 19
0
votes
0
answers
19
views
Have an issue with types when creating a Fastify plugin to decorate mongoose models using Zod
I have created a Fastify plugin to decorate Mongoose models, adding them to the Fastify interface:
declare module 'fastify' {
export interface FastifyInstance {
models: {
[key: ...
- 575
2
votes
1
answer
35
views
What’s the meaning of `T extends readonly unknown[] | []` in TypeScript’s function signature of `Promise.all`?
I noticed an interesting (possibly hacking) part in TypeScript’s lib.d.ts:
interface PromiseConstructor {
/* ... */
/**
* Creates a Promise that is resolved with an array of results when all ...
- 369
1
vote
1
answer
31
views
How to predict `type instatiation too deep and possibly infinite` error?
I'm trying to improve my knowledge of types in typescript, so I'm doing some type challenges. One of the challenges is to make a type that capitalises a generic string, as shown below (here).
type ...
0
votes
0
answers
53
views
Merging class definition with generic type definition
So say there is a type or interface that defines properties of actions, for example:
export interface AnimalActions {
jump: { height: number }
move: { speed: number, offset: number }
}
And there ...
- 5,961
1
vote
1
answer
86
views
Replicating the mongodb project aggregation in Typescript
My scenario: I am trying to build a typesafe wrapper around node-mongodb driver. I am having a hard time figuring out the return type for project aggregation stage.
Have a look at the TS Playground ...
- 145
0
votes
1
answer
52
views
How do I determine if a class's name exists as a key in a mapped object type?
I have a type that I'm trying to make dynamic. I currently have a hardcoded version that looks like this:
import type {
Text,
TextOptions,
} from 'pixi.js'
export type ConstructorParams<T ...
- 121
2
votes
1
answer
47
views
Can I make intellisense output more readable for Typescript generic with Omit
Context: I'm exposing a third party library to users, but needed to remove two properties from all functions in the library (we set them automatically). I've got a function to do that (and also run a ...
- 6,883
0
votes
0
answers
43
views
Vue 3 Generic Components: how to use a scoped slot with a generic data type inferred from an event listener prop
Click for Playground
<SideSheet>
<template #activator="{ onClick, ...slotProps }">
<v-btn
v-bind="slotProps"
@click="(e: PointerEvent) => ...
- 313
0
votes
1
answer
23
views
How to use Typescript Generics to infer type of object property
Given this simplified example code:
type People = {
[key: string]: {
names: (string | number)[];
};
};
const people: People = {
bert: {
names: ["Bert", 1],
},...
- 3
1
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0
answers
28
views
Generics Airthmetic in Typescript [duplicate]
I am a beginner in Typescript. I am trying to learn generics.
type Summable = string | number;
interface Calculation<Type> {
number1: Type;
number2: Type;
operation(): Type;
}
class ...
- 53