MCQs on TypeScript Compiler and Configuration | TypeScript

Explore advanced TypeScript configuration options with these 30 multiple-choice questions. Dive into tsconfig.json settings, customizing the build process, and working with declaration files and d.ts for robust TypeScript projects.

Topic 1: Advanced tsconfig.json Settings (10 Questions)

1. Which of the following is the default value for strict in a tsconfig.json file?
   A) true
   B) false
   C) undefined
   D) none
2. What does the noImplicitAny option in tsconfig.json control?
   A) Ensures that variables must have a type assigned
   B) Allows any type for variables
   C) Disables implicit type inference
   D) Throws errors when any is used
3. Which tsconfig.json option specifies the target JavaScript version for compilation?
   A) target
   B) module
   C) outDir
   D) lib
4. In the tsconfig.json, which option allows you to specify the root directory for your TypeScript files?
   A) rootDir
   B) baseUrl
   C) include
   D) files
5. What does the skipLibCheck option in the tsconfig.json file do?
   A) Skips checking the types of declaration files (.d.ts)
   B) Skips compiling libraries
   C) Skips type checking of user files
   D) Skips library files during bundling
6. What is the default value of moduleResolution in tsconfig.json?
   A) node
   B) classic
   C) esnext
   D) none
7. How do you enable TypeScript’s source map generation in the tsconfig.json?
   A) "sourceMap": true
   B) "sourceMap": "true"
   C) "generateSourceMaps": true
   D) "sourceMapping": true
8. Which option in tsconfig.json controls whether to output the compiled JavaScript to a different directory?
   A) outDir
   B) rootDir
   C) destinationDir
   D) outputDir
9. In tsconfig.json, what does setting "esModuleInterop": true do?
   A) Allows default import of CommonJS modules
   B) Enables strict mode for ES Modules
   C) Allows imports from external modules
   D) Ensures compatibility with ES6 module syntax
10. How do you prevent TypeScript from emitting JavaScript files after compilation in tsconfig.json?
    A) "noEmit": true
    B) "emit": false
    C) "generate": false
    D) "noCompile": true

Topic 2: Customizing Build Processes (10 Questions)

11. How can you specify a custom file for TypeScript’s build output?
    A) Use the --outFile compiler option
    B) Modify the outDir setting in tsconfig.json
    C) Set outputFile in tsconfig.json
    D) Use --output flag in the TypeScript command
12. Which option can be used to watch for file changes during TypeScript compilation?
    A) --watch
    B) --auto
    C) --watchFiles
    D) --autoCompile
13. What does the declaration option in tsconfig.json do?
    A) Generates declaration files (.d.ts) for TypeScript files
    B) Specifies the type definitions used in the project
    C) Declares the global variables for the project
    D) Generates JavaScript files
14. Which of the following options in tsconfig.json allows for incremental compilation?
    A) "incremental": true
    B) "cache": true
    C) "fastCompilation": true
    D) "optimized": true
15. How do you configure TypeScript to clean up old .tsbuildinfo files?
    A) "cleanUp": true
    B) "removeBuildInfo": true
    C) "tsBuildInfo": false
    D) "deleteOldBuildInfo": true
16. What does the exclude field in tsconfig.json control?
    A) Files to exclude from compilation
    B) Files to include in the compilation
    C) File extensions to exclude
    D) Files to include in declaration generation
17. Which TypeScript compiler flag allows specifying the module system to use?
    A) --module
    B) --target
    C) --moduleResolution
    D) --moduleSystem
18. How can you enable a strict mode that applies a variety of stricter checks?
    A) "strict": true
    B) "strictMode": true
    C) "strictChecks": true
    D) "strictErrors": true
19. What is the effect of setting the removeComments option to true in tsconfig.json?
    A) Removes comments from the output JavaScript files
    B) Prevents comments from being included in the source
    C) Keeps comments in the declaration files
    D) Removes comments from TypeScript files only
20. How can you specify multiple root directories in the tsconfig.json?
    A) Use the rootDirs option
    B) Use multiple rootDir options
    C) Use baseDirs option
    D) Use the include field with multiple directories

Topic 3: Declaration Files and d.ts (10 Questions)

21. What is the primary purpose of declaration files (.d.ts) in TypeScript?
    A) To provide type information for JavaScript libraries
    B) To generate type definitions from TypeScript code
    C) To exclude certain modules from TypeScript compilation
    D) To output JavaScript files from TypeScript
22. How can you include an external .d.ts file in a TypeScript project?
    A) Use the /// <reference path="file.d.ts" /> directive
    B) Use the import statement
    C) Include it in the include array in tsconfig.json
    D) Both A and C
23. What happens if you don’t include .d.ts files when using JavaScript libraries in TypeScript?
    A) TypeScript will generate types automatically
    B) TypeScript will treat the libraries as any
    C) TypeScript will throw an error during compilation
    D) TypeScript will ignore the library
24. What is the correct syntax for declaring a global variable in a .d.ts file?
    A) declare var globalVar: string;
    B) export var globalVar: string;
    C) global var globalVar: string;
    D) declare global { var globalVar: string; }
25. How do you specify the type of a third-party module using a declaration file?
    A) declare module 'module-name' { export type myType; }
    B) declare module 'module-name' { export default myType; }
    C) module 'module-name' { export type myType; }
    D) export module 'module-name' { type myType; }
26. What is the correct way to declare a function in a .d.ts file?
    A) declare function myFunction(): void;
    B) export function myFunction(): void;
    C) declare myFunction(): void;
    D) function declare myFunction(): void;
27. How can you define an interface in a declaration file?
    A) declare interface MyInterface {}
    B) interface MyInterface {}
    C) export interface MyInterface {}
    D) declare type MyInterface = {};
28. Can you use declare in a .d.ts file to define an external module?
    A) Yes, with the declare module keyword
    B) No, declare is only used for variables
    C) Yes, but only for global modules
    D) No, modules must be declared in the tsconfig.json
29. In a declaration file, what does the export keyword do?
    A) Makes the declared type or function available for import
    B) Prevents the type or function from being used outside
    C) Declares a module for external usage
    D) Makes the function or variable globally available
30. What is the correct syntax for importing a .d.ts file in TypeScript?
    A) import './file.d.ts';
    B) import { typeName } from './file.d.ts';
    C) /// <reference path="file.d.ts" />
    D) import 'file.d.ts';

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