TYPESCRIPT · EASY CODEX

TypeScript Interview Questions — Easy

Q: What is TypeScript? Compare it with JavaScript.

Definition: TypeScript is a strongly typed, static superset of JavaScript developed by Microsoft. It compiles down to plain JavaScript. Static Typing: Checks and validates types during compilation, wh

Q: Compare dynamic, static, and structural typing.

Dynamic Typing (JS): Variable types are resolved at runtime. Variables can freely change types. Static Typing (TS): Variable types are declared and enforced during compile-time. Re-assigning an incomp

Q: Compare `any`, `unknown`, `never`, and `void` in TypeScript.

any: Turns off all compile-time type checking. Highly unsafe; permits accessing any property or calling any method. unknown: Type-safe counterpart to any. Allows holding any value, but bars any operat

Q: Compare Interfaces and Type Aliases.

Declaration Merging: Interfaces can be re-declared and automatically merge properties. Type Aliases throw "duplicate identifier" errors. Extensibility: Interfaces extend other interfaces/types via ext

Q: What are Type Assertions? Why can they be dangerous?

Definition: Bypasses the compiler's automatic type inference, manually informing the compiler of a specific type (using value as Type or <Typevalue). Danger: Type assertions do not run runtime casting

Core concepts, definitions, basic syntax, and first principles expected in round 1 screening.

50 Theory Questions7 Implementation Folios5 Free Model Answers

THEORY QUESTIONS & SOLUTIONSShowing 5 of 50 questions

Q1What is TypeScript? Compare it with JavaScript.

Definition: TypeScript is a strongly typed, static superset of JavaScript developed by Microsoft. It compiles down to plain JavaScript.
Static Typing: Checks and validates types during compilation, whereas JavaScript resolves types dynamically at runtime.
Error Detection: Catches syntax and type-mismatch bugs in the IDE/compiler before execution.
Tooling: Provides superior IDE support (advanced autocomplete, safe refactoring, and parameter signatures).

Q2Compare dynamic, static, and structural typing.

Dynamic Typing (JS): Variable types are resolved at runtime. Variables can freely change types.
Static Typing (TS): Variable types are declared and enforced during compile-time. Re-assigning an incompatible type causes a compile error.
Structural Typing (TS): Types are compared based on their shape/structure rather than explicit nominal declarations (duck typing: "if it looks like a duck, it is a duck").

Q3Compare `any`, `unknown`, `never`, and `void` in TypeScript.

any: Turns off all compile-time type checking. Highly unsafe; permits accessing any property or calling any method.
unknown: Type-safe counterpart to any. Allows holding any value, but bars any operations (property access/calls) until the type is narrowed.
void: Indicates the complete absence of a return value (typically used for functions with side effects).
never: Represents values that will never occur (e.g., functions that throw errors or enter infinite loops).

Q4Compare Interfaces and Type Aliases.

Declaration Merging: Interfaces can be re-declared and automatically merge properties. Type Aliases throw "duplicate identifier" errors.
Extensibility: Interfaces extend other interfaces/types via extends. Type Aliases compose via intersection operators (&).
Capabilities: Type Aliases can describe unions, primitives, tuples, and mapped types directly. Interfaces are strictly limited to object/class shapes.

Q5What are Type Assertions? Why can they be dangerous?

Definition: Bypasses the compiler's automatic type inference, manually informing the compiler of a specific type (using value as Type or <Type>value).
Danger: Type assertions do not run runtime casting/conversions. If the runtime value does not match the asserted compile-time type, it can crash during execution with silent type mismatches.

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