INTERVIEW QUESTIONS

TypeScript Interview Questions

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TYPESCRIPT

What is TypeScript and how does it differ from JavaScript?

TypeScript is a statically typed superset of JavaScript developed by Microsoft. It adds optional type annotations, compile-time type checking, interfaces, and modern ECMAScript features. Unlike JavaScript, which is dynamically typed and evaluated at runtime, TypeScript code is compiled (transpiled) into plain JavaScript that can run in any browser or Node.js environment.

CompanyMicrosoft◦ Fundamentals

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TYPESCRIPT

What is the difference between interface and type alias in TypeScript?

Both define custom object shapes, but interfaces support declaration merging (multiple definitions with the same name merge their properties) and extend syntax with better compiler performance for object hierarchies. Type aliases can represent unions, primitives, tuples, and mapped types directly, but cannot be reopened or declaration-merged.

CompanyGoogle◦ Types & Interfaces

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TYPESCRIPT

What is the any type, and why should its usage be minimized?

The 'any' type disables compile-time type checking for a variable, allowing any property access, method invocation, or reassignment. Overusing 'any' defeats the primary purpose of TypeScript, masking potential runtime errors, degrading IDE auto-completion, and propagating untyped values throughout the codebase.

CompanyAmazon◦ Type Safety

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TYPESCRIPT

What is the difference between any and unknown in TypeScript?

'any' allows any operation without type checking. 'unknown' is the type-safe counterpart: while any value can be assigned to 'unknown', you cannot access properties, call methods, or instantiate it without first performing type narrowing (using typeof, instanceof, or custom type guards).

CompanyMeta◦ Type Safety

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TYPESCRIPT

What is the never type and when is it returned or used?

The 'never' type represents values that never occur. It is the return type for functions that always throw an exception or enter infinite loops. It is also used in exhaustive type checking within switch statements to ensure all union branches are handled at compile time.

CompanyStripe◦ Advanced Types

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