Interview Prep

TypeScript

250 questions across 16 categories

50 of 50 questions

#	Category	Question	Answer
1	Type System	What is the difference between 'type' and 'interface' in TypeScript? When should you prefer one over the other?	Click row to expand
2	Type System	Explain structural typing (duck typing) in TypeScript. How does it differ from nominal typing?	Click row to expand
3	Generics	What are generic constraints? Explain 'extends', 'keyof', and 'infer' in generic constraints.	Click row to expand
4	Utility Types	Explain these built-in utility types and implement each from scratch: Partial, Required, Readonly, Pick, Omit, Record.	Click row to expand
5	Type Narrowing	Explain TypeScript type narrowing. What are the different narrowing techniques and how does control flow analysis work?	Click row to expand
6	Type Narrowing	What are discriminated unions? How do you use them with exhaustive checks and the never type?	Click row to expand
7	Advanced Types	What are mapped types? Explain how to use them to create transformation types with modifiers.	Click row to expand
8	Advanced Types	What are conditional types? Explain distributivity over unions and how to prevent it.	Click row to expand
9	Advanced Types	What are template literal types? Provide practical examples of type-safe string manipulation.	Click row to expand
10	Advanced Types	What are recursive types in TypeScript? What are their limitations and how do you handle deeply nested types?	Click row to expand
11	Generics	What is variance in generic types? Explain covariance, contravariance, and invariance with TypeScript examples.	Click row to expand
12	Generics	Explain higher-kinded types simulation in TypeScript using the HKT pattern.	Click row to expand
13	Generics	What is the Awaited<T> utility type? How do you handle deeply nested Promise types?	Click row to expand
14	Advanced Types	How do you type a tuple type in TypeScript? What are variadic tuple types and how do they enable type-safe currying?	Click row to expand
15	Decorators	What are TypeScript decorators? Explain class, method, property, and parameter decorators. What changes in decorators v2 (Stage 3)?	Click row to expand
16	Configuration	Explain the most important tsconfig.json compiler options for strict production TypeScript.	Click row to expand
17	Type System	What is the 'unknown' type? How does it differ from 'any', and when should you use it?	Click row to expand
18	Type System	What is declaration merging in TypeScript? How is it used for module augmentation?	Click row to expand
19	Advanced Types	What is satisfies operator (TypeScript 4.9)? How does it differ from type annotation and 'as'?	Click row to expand
20	Advanced Types	Explain the Extract and Exclude utility types. How do you use them to manipulate union types?	Click row to expand
21	Type System	What is 'as const' assertion? How does it differ from readonly and how does it enable literal type inference?	Click row to expand
22	Configuration	What is the TypeScript project references feature? When and how should you use it for monorepo setups?	Click row to expand
23	Type System	What are ambient types and .d.ts files? How do you write type declarations for a JavaScript library that has no types?	Click row to expand
24	Generics	How do you implement a type-safe event emitter with generic TypeScript? What pattern enables type-safe event names and payloads?	Click row to expand
25	Advanced Types	What is the NoInfer utility type (TypeScript 5.4)? What problem does it solve?	Click row to expand
26	Type System	What is excess property checking and when does TypeScript bypass it?	Click row to expand
27	Advanced Types	How do you implement a deep merge type in TypeScript? What are the recursive type challenges?	Click row to expand
28	Configuration	What are TypeScript path mappings and module resolution? Explain 'node', 'node16', and 'bundler' strategies.	Click row to expand
29	Type System	What are opaque/branded types in TypeScript? How do they prevent type confusion between semantically different string or number types?	Click row to expand
30	Advanced Types	How do you use TypeScript with React? Explain typing children, event handlers, generics in components, and forwardRef.	Click row to expand
31	Type System	What is the 'infer' keyword in conditional types? Provide three advanced use cases.	Click row to expand
32	Advanced Types	How do you implement a type-safe builder pattern in TypeScript that ensures required fields are set before build() is called?	Click row to expand
33	Type System	What is declaration space and how do types and values coexist in TypeScript?	Click row to expand
34	Generics	What is the ReturnType, InstanceType, and Parameters utility types? How do you use them to derive types from existing code?	Click row to expand
35	Advanced Types	How does TypeScript handle circular type dependencies? What patterns cause infinite recursion and how do you fix them?	Click row to expand
36	Configuration	What is isolatedModules in tsconfig and why is it required by tools like Vite and esbuild?	Click row to expand
37	Type System	What are assertion functions in TypeScript? How do they differ from type predicates?	Click row to expand
38	Advanced Types	What is the accessor keyword and private class fields (#)? How do they differ from TypeScript's private keyword?	Click row to expand
39	Type System	How does TypeScript handle index signatures and Record types? What are the tradeoffs?	Click row to expand
40	Generics	What is generic inference from default values and from return types? How does TypeScript infer type parameters from usage context?	Click row to expand
41	Type System	What are utility types ReturnType, Awaited, and OmitThisParameter? How do they compose for async method typing?	Click row to expand
42	Advanced Types	What is the 'using' keyword and Symbol.dispose (TypeScript 5.2)? How does it improve resource management?	Click row to expand
43	Type System	How do you model algebraic data types (ADTs) in TypeScript? Explain product types and sum types.	Click row to expand
44	Configuration	What is verbatimModuleSyntax (TypeScript 5.0)? How does it affect import/export behavior?	Click row to expand
45	Advanced Types	How do you type a Redux-like state management system in TypeScript with type-safe actions and reducers?	Click row to expand
46	Type System	What is module augmentation vs global augmentation? When would you use each?	Click row to expand
47	Generics	What is TypeScript's function overloading? When does it help and when does it lead to complexity?	Click row to expand
48	Configuration	What is type checking performance? What tsconfig settings and code patterns slow down TypeScript, and how do you fix them?	Click row to expand
49	Type System	How do you migrate a large JavaScript codebase to TypeScript? What strategy minimizes disruption?	Click row to expand
50	Advanced Types	What is the difference between unknown, never, any, and void in TypeScript? When is each appropriate?	Click row to expand