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Stripe · Typescript
Practice Typescript questions specifically asked in Stripe interviews – ideal for online test preparation, technical rounds and final HR discussions.
Questions
9
Tagged for this company + subject
Company
Stripe
View company-wise questions
Subject
Typescript
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Go through each question and its explanation. Use this page for targeted revision just before your Stripe Typescript round.
In mapped types, “-?” removes optional, “+?” adds optional. Similarly, “-readonly” removes readonly and “+readonly” adds it.
type Requiredify<T> = { [K in keyof T]-?: T[K] };
// { a?: number } -> { a: number }For complete preparation, combine this company + subject page with full company-wise practice and subject-wise practice. You can also explore other companies and topics from the links below.
Interfaces extend and merge naturally and work cleanly with classes. Use type aliases for unions, intersections, and advanced mapped/conditional types.
interface Animal { speak(): void }
class Dog implements Animal { speak() { /*...*/ } }Express Request is fully generic: `Request<Params, ResBody, ReqBody, Query>`. You can type each part precisely and get IntelliSense everywhere.
import { Request, Response } from 'express';
function handler(req: Request<{id:string}, any, {name:string}, {q?:string}>, res: Response){
res.json({ ok: true });
}TypeScript uses structural typing: two types are compatible if their required members line up, regardless of their declared names. This applies across interfaces, type aliases, and classes treated as shapes.
type Point = { x: number; y: number }
interface Coords { x: number; y: number }
const p: Point = { x: 1, y: 2 };
const c: Coords = p; // ✅ structural compatibilityParameters<T> gives the parameter tuple type of a function. ConstructorParameters<T> does the same for class constructors.
function f(a: string, b: number) {}
type P = Parameters<typeof f>; // [string, number]You can reopen a module’s declaration in a `.d.ts` file and add missing types or members. This is great for patching third-party typings without editing `node_modules`.
/* types/lib-augment.d.ts */
declare module 'some-lib' {
export function fancy(): string;
}Use `super(...)` as the first statement in the subclass constructor to run the base class initialization.
class A { constructor(public id: string) {} }
class B extends A { constructor(){ super('b'); } }Tuples model a fixed-length, ordered list where each index can have its own type (e.g., `[string, number]`). They can be mutable or readonly, and tuple elements can even be optional.
type Pair = [string, number]; const p: Pair = ['x', 1]; // Optional element example: type Log = [string, number?];
Interfaces describe the shape (what methods/properties exist). Classes provide the actual code (how they work) and can implement interfaces.
interface Repo { get(id: string): Promise<string> }
class MemoryRepo implements Repo { async get(id: string){ return id; } }