TypeScript Technology & Digital Tools 4 — Questions and Answers
Question 1: Which Jest configuration is needed to run TypeScript tests without a separate compile step?
- ts-jest or babel-jest with @babel/preset-typescript (Correct answer)
- jest-typescript
- tsc-jest
- type-jest
Correct answer: ts-jest or babel-jest with @babel/preset-typescript
`ts-jest` or `babel-jest` with the TypeScript preset transforms `.ts` files on-the-fly so Jest can execute them.
Question 2: What does the `moduleResolution` option `bundler` (added in TypeScript 5.0) enable?
- CommonJS-style resolution
- Resolution logic matching modern bundlers like Vite and esbuild, supporting package.json exports (Correct answer)
- Node 10-style resolution
- Resolution of `.d.ts` files only
Correct answer: Resolution logic matching modern bundlers like Vite and esbuild, supporting package.json exports
`moduleResolution: bundler` aligns TypeScript's import resolution with tools like Vite and webpack that use `package.json` `exports` fields.
Question 3: Which tool can automatically add missing `@types/*` packages to a project based on imported modules?
- typesync (Correct answer)
- typecheck
- dts-gen
- typedoc
Correct answer: typesync
`typesync` scans your `package.json` dependencies and installs any missing `@types/*` packages from DefinitelyTyped.
Question 4: What is the advantage of using `esbuild` over `tsc` for production builds in large TypeScript projects?
- esbuild performs full type checking
- esbuild transpiles TypeScript significantly faster by stripping types without type checking (Correct answer)
- esbuild supports decorators natively
- esbuild generates smaller declaration files
Correct answer: esbuild transpiles TypeScript significantly faster by stripping types without type checking
esbuild is written in Go and strips TypeScript types without running the type checker, making builds 10-100× faster than `tsc`.
Question 5: What does the `composite` option in `tsconfig.json` enable?
- Enables project references and incremental builds across multiple TypeScript subprojects (Correct answer)
- Composes multiple tsconfig files
- Enables strict mode across all files
- Creates composite type unions automatically
Correct answer: Enables project references and incremental builds across multiple TypeScript subprojects
`composite: true` is required for TypeScript project references, enabling incremental builds that only recompile changed subprojects.
Question 6: Which command generates TypeScript declaration files from an existing JavaScript library?
- tsc --declaration
- npx dts-gen -m <module-name> (Correct answer)
- typegen --module
- ts-node --dts
Correct answer: npx dts-gen -m <module-name>
`dts-gen` inspects a JavaScript module at runtime and generates a starter `.d.ts` declaration file.
Question 7: What is `TypeDoc` used for in a TypeScript project?
- Type-checking at runtime
- Generating HTML API documentation from TypeScript source code and JSDoc comments (Correct answer)
- Validating JSON schemas against TypeScript types
- Running end-to-end tests
Correct answer: Generating HTML API documentation from TypeScript source code and JSDoc comments
TypeDoc parses TypeScript source and JSDoc annotations to produce browsable API reference documentation.
TypeScript Technology & Digital Tools 4
Which Jest configuration is needed to run TypeScript tests without a separate compile step?