TypeScript Project Planning & Execution 3

Question 1

Which tool is commonly used to enforce consistent TypeScript code style and catch common bugs beyond what the compiler checks?

Accepted Answer

ESLint with @typescript-eslint

Answer

The `@typescript-eslint` plugin extends ESLint with TypeScript-aware rules for linting patterns the compiler doesn't flag.

Question 2

In a TypeScript project, what is the purpose of a `.d.ts` declaration file?

Accepted Answer

To provide type information for JavaScript libraries without source code

Answer

Declaration files (`.d.ts`) expose type definitions for libraries so TypeScript consumers get autocomplete and type safety.

Question 3

Your team uses `strict: true` in tsconfig. Which individual flag does this NOT enable?

Accepted Answer

noUnusedLocals

Answer

`noUnusedLocals` is a separate flag not included in `strict: true`; it must be opted into independently.

Question 4

Which approach correctly types a React component's props in a TypeScript project to enforce required vs optional fields?

Accepted Answer

Define an interface with optional properties using `?` and required ones without

Answer

TypeScript interfaces with `?` for optional properties and required fields without it give components precise type safety.

Question 5

What does enabling `isolatedModules: true` in tsconfig prevent, and why is it important for tools like Babel?

Accepted Answer

It disallows const enums and namespace imports that require full-program analysis

Answer

`isolatedModules` disallows TypeScript features that Babel (which transpiles file-by-file) cannot handle without full-program context.

TypeScript Practice Test