TypeScript Quality Assurance & Improvement 2

Question 1

Which TypeScript compiler option enforces that all switch statement cases are exhaustively handled for union types?

Accepted Answer

never type in default branch

Answer

Using the `never` type in the default branch of a switch causes a compile-time error if any union member is unhandled.

Question 2

What is the purpose of `readonly` arrays (`ReadonlyArray<T>`) in TypeScript QA practices?

Accepted Answer

They prevent accidental mutation of array contents

Answer

`ReadonlyArray<T>` prevents mutation methods like `push` or `splice` from being called, catching unintended side effects at compile time.

Question 3

Which tool is commonly used to enforce consistent TypeScript code style and catch potential bugs through static analysis?

Accepted Answer

ESLint with @typescript-eslint plugin

Answer

ESLint with the `@typescript-eslint` plugin provides TypeScript-aware linting rules that catch type-related issues and enforce style.

Question 4

What does enabling `strict` mode in tsconfig.json actually do?

Accepted Answer

It enables a set of strict type-checking flags including strictNullChecks and noImplicitAny

Answer

`strict: true` is shorthand for enabling strictNullChecks, noImplicitAny, strictFunctionTypes, strictBindCallApply, and several other flags simultaneously.

Question 5

In TypeScript testing, what is the benefit of using `as const` assertions on test fixture objects?

Accepted Answer

It narrows the type to literal types, preventing accidental value changes in fixtures

Answer

`as const` makes all properties readonly with literal types, ensuring test fixtures aren't accidentally modified between tests.

TypeScript Practice Test

TypeScript Practice Test

TypeScript Quality Assurance & Improvement 2