Which of the following is the correct file extension for standard TypeScript files?
1. Which of the following is the correct file extension for standard TypeScript files?
- A..typescript
- B..tscript
- C..ts
- D..tsx-only
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TypeScript - Basics
Optional properties, strict mode, type narrowing, access modifiers, and tsconfig configuration.
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What is the difference between `any` and `unknown` in TypeScript?
2. What is the difference between `any` and `unknown` in TypeScript?
- A.any requires type checking; unknown does not.
- B.unknown only accepts string or number; any accepts all types.
- C.unknown requires type checking/assertion before performing operations; any does not.
- D.There is no difference; they are aliases.
What is TypeScript?
3. What is TypeScript?
- A.A complete replacement for JavaScript that runs directly in all browsers
- B.A database query language for web applications
- C.A typed superset of JavaScript that compiles to plain JavaScript
- D.A styling library that extends CSS functionalities
What does the `void` type indicate when used as a function return type?
4. What does the `void` type indicate when used as a function return type?
- A.The function returns null only.
- B.The function can return any type.
- C.The function does not return any value.
- D.The function will never complete or terminate.
What does the `never` type represent in TypeScript?
5. What does the `never` type represent in TypeScript?
- A.Null and undefined values
- B.Variables that are declared but not initialized
- C.Values that will never occur (e.g. from functions that throw errors)
- D.Variables that can change their types dynamically
What is the standard configuration file used to configure a TypeScript project?
6. What is the standard configuration file used to configure a TypeScript project?
- A.typescript.config
- B.ts-config.xml
- C.tsconfig.json
- D.tsconfig.js
What does the `any` type represent in TypeScript?
7. What does the `any` type represent in TypeScript?
- A.A type representing only empty values like null and undefined
- B.A placeholder type representing only arrays and objects
- C.A type that disables type checking, allowing any type of value
- D.A union type of string and number only
How do you specify a type annotation for a variable `age` as a number in TypeScript?
8. How do you specify a type annotation for a variable `age` as a number in TypeScript?
- A.let age = number;
- B.let number age;
- C.let age: number;
- D.let age: Int;
Which command is used to run the TypeScript compiler and compile files?
9. Which command is used to run the TypeScript compiler and compile files?
- A.typescript-compile
- B.ts-run
- C.tsc
- D.compile-ts
How do you define a Union Type that allows a variable `id` to be either a string or a number?
10. How do you define a Union Type that allows a variable `id` to be either a string or a number?
- A.let id: string & number;
- B.let id: string or number;
- C.let id: string | number;
- D.let id: [string, number];
Which keyword is used to prevent a property of an interface or class from being reassigned after initialization?
11. Which keyword is used to prevent a property of an interface or class from being reassigned after initialization?
- A.const
- B.private
- C.readonly
- D.static
How do you annotate a parameter `name` as a string in a TypeScript function declaration?
12. How do you annotate a parameter `name` as a string in a TypeScript function declaration?
- A.function greet(string name) { }
- B.function greet(name = string) { }
- C.function greet(name: string) { }
- D.function greet(:string name) { }
How do you declare an optional parameter `email` in a function signature in TypeScript?
13. How do you declare an optional parameter `email` in a function signature in TypeScript?
- A.function registerUser(name: string, optional email: string) { }
- B.function registerUser(name: string, email: string?) { }
- C.function registerUser(name: string, email?: string) { }
- D.function registerUser(name: string, email: string = optional) { }
Which keyword is used to define a structural contract/shape of an object in TypeScript?
14. Which keyword is used to define a structural contract/shape of an object in TypeScript?
- A.typealias
- B.contract
- C.interface
- D.struct
How do you declare a default value for a parameter `role` in a TypeScript function?
15. How do you declare a default value for a parameter `role` in a TypeScript function?
- A.function createUser(name: string, role?: string "member") { }
- B.function createUser(name: string, role: string default "member") { }
- C.function createUser(name: string, role: string = "member") { }
- D.function createUser(name: string, role: string("member")) { }
What is a major difference between Interface and Type Alias in TypeScript?
16. What is a major difference between Interface and Type Alias in TypeScript?
- A.Type aliases support inheritance using 'extends'; interfaces do not.
- B.Interfaces can represent union types; type aliases cannot.
- C.Interfaces can participate in declaration merging; type aliases cannot.
- D.Interfaces compile to JavaScript classes; type aliases are removed.
Which keyword is used to declare a Type Alias in TypeScript?
17. Which keyword is used to declare a Type Alias in TypeScript?
- A.interface
- B.alias
- C.type
- D.define
Which operator is used to combine multiple types into one (Intersection Type)?
18. Which operator is used to combine multiple types into one (Intersection Type)?
- A.|
- B.&&
- C.&
- D.+
How do you define the return type of a function as a boolean in TypeScript?
19. How do you define the return type of a function as a boolean in TypeScript?
- A.function isEven(n: number: boolean) { return true; }
- B.function isEven(n: number) return boolean { return true; }
- C.function isEven(n: number): boolean { return true; }
- D.function boolean isEven(n: number) { return true; }
How do you mark a property `middleName` as optional within an interface?
20. How do you mark a property `middleName` as optional within an interface?
- A.interface User { optional middleName: string; }
- B.interface User { middleName: string | null; }
- C.interface User { middleName?: string; }
- D.interface User { middleName: string?; }
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