Chapter quiz · Real-World TypeScript

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8 questions on Real-World TypeScript. Pass 70% to clear the chapter.

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Quiz

TS Real-World — Chapter Quiz

Eight questions on tsconfig, modules, declaration files, React/Node, and migration.

0/ 9

Question 1
1
What does strict: true in tsconfig.json do?
ASpeeds up compilationBEnables the family of strict type-check flags at onceCDisables JS interopDStops the build on any warning
strict: true is an umbrella flag — it turns on noImplicitAny, strictNullChecks, strictFunctionTypes, and more. Always on for new code.
Question 2
2
What kind of file is .d.ts?
AA compiled JS outputBA type declaration file — describes shapes without implementationCA test fileDA documentation file
.d.ts files contain type declarations only — no runtime code. The @types/... packages are full of them.
Question 3
3
TypeScript types are erased at compile time and cannot validate runtime input.
TTrueFFalse
For runtime validation (HTTP bodies, env vars, JSON), use a runtime schema library like Zod.
Question 4
4
What is the modern import syntax for type-only imports?
Aimport { type X } or import type { X }Bimport.type XCrequire<type>(X)DSame as a regular import
Both forms work. With verbatimModuleSyntax, explicit type imports are required so TS knows to erase them.
Question 5
5
The library ___ pairs a runtime schema with a TS-inferred type, perfect for system-boundary validation.
Zod schemas validate runtime data and you derive the TS type via z.infer<typeof Schema> — one source of truth.
Question 6
6
In React + TS, what does useRef<HTMLInputElement>(null) return?
AAn HTMLInputElementBA RefObject<HTMLInputElement | null>Cnull foreverDA string
The ref's .current is HTMLInputElement | null until the element mounts — forcing you to handle the null case.
Question 7
7
What's the recommended way to migrate a large JS codebase to TS?
ARewrite everything in one big PRBEnable allowJs, convert files incrementally, tighten flags over timeCAbandon the codebaseDConvert tests first, then ignore the rest
Gradual migration is the supported path — allowJs lets JS and TS coexist; you tighten strict flags one at a time.
Question 8
8
Which of these belong in a tsconfig.json for a modern bundler-based project?
Select all that apply.
A"moduleResolution": "Bundler"B"strict": trueC"noEmit": trueD"target": "ES3"E"isolatedModules": true
Bundler resolution, strict mode, noEmit (the bundler handles compilation), and isolatedModules are the modern defaults. ES3 is hopelessly outdated.