TypeScript Quiz

To pass the quiz, you must correctly answer at least 18 of the 20 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- What is TypeScript? #### --distractors-- A framework used for system programming. --- A database management tool. --- A programming language used for styling websites. #### --answer-- A superset of JavaScript that adds static typing. ### --question-- #### --text-- Why should TypeScript be used in a project? #### --distractors-- It eliminates the need for testing in applications. --- It is faster than all other programming languages. --- It makes styling websites easier. #### --answer-- It improves maintainability by adding type definitions to JavaScript. ### --question-- #### --text-- What language is TypeScript compiled down to? #### --distractors-- Java --- Python --- C++ #### --answer-- JavaScript ### --question-- #### --text-- What would be the output of the following code snippet? ```ts function sum(a: number, b: number): number { return a + b; } console.log(sum(2, 3)); ``` #### --distractors-- `2 + 3` --- `undefined` --- `Error: Type 'number' is not assignable to type 'string'` #### --answer-- `5` ### --question-- #### --text-- What is the primary purpose of an interface in TypeScript? #### --distractors-- To compile TypeScript code into JavaScript. --- To create a new data type. --- To create a new JavaScript Object. #### --answer-- To define the structure of an object. ### --question-- #### --text-- Which of the following is NOT a basic primitive in TypeScript? #### --distractors-- string --- boolean --- number #### --answer-- array ### --question-- #### --text-- Which of the following correctly defines a literal type in TypeScript? #### --distractors-- `let y: string;` --- `let z: boolean;` --- `let a: number[];` #### --answer-- `let x: 5;` ### --question-- #### --text-- What is the primary purpose of the `type` keyword in TypeScript? #### --distractors-- To declare variables. --- To create classes. --- To implement interfaces. #### --answer-- To define custom types. ### --question-- #### --text-- Which of the following correctly defines a union type? #### --distractors-- `type Result = Pass && Fail;` --- `type Result = Pass & Fail;` --- `type Result = Pass + Fail;` #### --answer-- `type Result = Pass | Fail;` ### --question-- #### --text-- Which of the following capabilities is unique to `interface` and CANNOT be achieved using `type` in TypeScript? #### --distractors-- Defining object shapes. --- Creating union types. --- Defining types that include only specific values. #### --answer-- Declaring class implementations. ### --question-- #### --text-- What is the primary purpose of using generics in TypeScript? #### --distractors-- To implement inheritance between classes. --- To define structure of an object. --- To create a new data type. #### --answer-- To write reusable code that can work with multiple types. ### --question-- #### --text-- Which of the following is a **proper example** of a generic function in TypeScript? #### --distractors-- `function add(a: number, b: number): number { return a + b; }` --- `function multiply(a: number, b: number): { return a * b; }` --- `function getValue<T>(value: any): any { return value; }` #### --answer-- `function identity<T>(value: T): T { return value; }` ### --question-- #### --text-- What is type narrowing in TypeScript? #### --distractors-- Reducing the size of compiled JavaScript. --- Limiting the number of types in a union. --- Removing unused types from a TypeScript project. #### --answer-- To write code that narrows down a union type to a more specific type. ### --question-- #### --text-- Which file is typically used to configure TypeScript compiler options? #### --distractors-- `package.json` --- `package.config.json` --- `typescript.config.js` #### --answer-- `tsconfig.json` ### --question-- #### --text-- What does the `rootDir` option in the `tsconfig.json` file specify? #### --distractors-- The version of TypeScript to use during compilation. --- The target runtime environment (e.g., Node.js or browser) for the TypeScript code. --- The specific module system to use for imports and exports. #### --answer-- The directory that holds your source files. ### --question-- #### --text-- Which example uses `instanceof` correctly to narrow the type to access the `value` property safely? #### --distractors-- ```ts const email = document.querySelector("#email"); if (email instanceof <input>) { console.log(email.value); } ``` --- ```ts const email = document.querySelector("#email"); if (email instanceof Element) { console.log(email.value); } ``` --- ```ts const email = document.querySelector("#email"); if (email instanceof <HTMLInputElement>) { console.log(email.value); } ``` #### --answer-- ```ts const email = document.querySelector("#email"); if (email instanceof HTMLInputElement) { console.log(email.value); } ``` ### --question-- #### --text-- What does setting `"strict": true` in `tsconfig.json` do in TypeScript? #### --distractors-- Enables static type check so that you can catch the mistakes before you run your code. --- Enforces you to always use ES6 syntax. --- Enforces you to compile the code before you run it. #### --answer-- Enables a set of type-checking options such as requiring handling of `null` or `undefined` and preventing implicit `any`. ### --question-- #### --text-- What is the purpose of the `never` type in TypeScript? #### --distractors-- To represent null or undefined. --- To represent any possible value. --- To represent a type that can be anything except null. #### --answer-- To represent the type of values that never occur. ### --question-- #### --text-- Which of the following `getRandomValue` function calls will compile successfully in TypeScript? ```ts const getRandomValue = (array: string[]) => { return array[Math.floor(Math.random() * array.length)]; } ``` #### --distractors-- `getRandomValue([1, 2, 3])` --- `getRandomValue("ABC")` --- `getRandomValue({A: "A", B: "B", C: "C"})` #### --answer-- `getRandomValue(["A", "B", "C"])` ### --question-- #### --text-- How can you fix the TypeScript compiler error `'email' is possibly 'null'` in the following code using optional chaining? ```ts const email = document.querySelector<HTMLInputElement>("#email"); console.log(email.value); ``` #### --distractors-- `console.log(email?:value);` --- `console.log(email?value);` --- `console.log(email.?value);` #### --answer-- `console.log(email?.value);`