Question 1

What are TypeScript's primitive types?

Accepted Answer

string, number, boolean, null, undefined, symbol, bigint — plus special any/unknown/never/void. Prefer precise primitives over any. Note number covers floats/ints; bigint is separate.

Question 2

any vs unknown vs never?

Accepted Answer

any disables checking; unknown is top type needing narrowing; never is empty/uninhabited. Prefer unknown for untrusted input. never appears in exhaustiveness and impossible returns.

Question 3

What is a union type and when do you use it?

Accepted Answer

A value that can be one of several types — model alternatives explicitly. Narrow with typeof/in/discriminants. Avoid huge untagged unions when objects differ.

Question 4

Intersection types — what are they for?

Accepted Answer

Combine types (A & B); useful for mixins and object composition. Conflicts in same property types can become never. Prefer interfaces for object extension often.

Question 5

type vs interface for object shapes?

Accepted Answer

Both describe objects; interfaces merge via declaration merging; type aliases can union/intersect freely. Team style often: interfaces for objects, types for unions/mapped. Be consistent.

Question 6

What are literal types?

Accepted Answer

Types that are specific values like 'admin' or 42; power discriminated unions. as const asserts widen-prevention. Useful for event names and config keys.

Question 7

Explain void vs undefined as return types.

Accepted Answer

void means callers shouldn't use the return value; undefined is the undefined value type. Callbacks typed void can return values still. Avoid void for variables storing undefined.

Question 8

How do tuples differ from arrays in TS?

Accepted Answer

Tuples have fixed length/position types; arrays are homogeneous variable length. Labeled tuple elements improve readability. Optional/rest elements supported.

Types TypeScript Interview Questions

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