JavaScript Fundamentals Quiz

To pass the quiz, you must correctly answer at least 18 of the 20 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- Which one of these will create a String object? #### --distractors-- ```js String({ "Hello World" }); ``` --- ```js String("Hello World"); ``` --- ```js "Hello World".toString(); ``` #### --answer-- ```js new String("Hello World"); ``` ### --question-- #### --text-- How can you convert a String object into a string literal? #### --distractors-- With the `String()` constructor. --- With the `.stringify()` method. --- Enclose the `String` object in double quotes. #### --answer-- With the `.toString()` method. ### --question-- #### --text-- Why can you use methods like `.length`, `.repeat()`, `.concat()`, and `.slice()` on a string primitive in JavaScript? #### --distractors-- Those methods exist natively on string primitives. --- String primitives are stored as objects internally. --- JavaScript temporarily converts the string primitive to an array. #### --answer-- JavaScript temporarily wraps the string primitive in a String object. ### --question-- #### --text-- What will the following code log to the console? ```js let stringArray = [8, 9, 10].toString(); console.log(stringArray); ``` #### --distractors-- `[8,9,10]` --- `["8", "9", "10"]` --- `"8", "9", "10"` #### --answer-- `"8,9,10"` ### --question-- #### --text-- Which of the following returns a `Number` object from the string `"123"`? #### --distractors-- `Object("123")` --- `"123".toNumber()` --- `Number("123")` #### --answer-- `new Number("123")` ### --question-- #### --text-- What will `Number(true)` and `Number(false)` return, respectively? #### --distractors-- `undefined` and `undefined` --- `NaN` and `NaN` --- `true` and `false` #### --answer-- `1` and `0` ### --question-- #### --text-- What will `Number(undefined)` and `Number(null)` return, respectively? #### --distractors-- `NaN` and `NaN` --- `0` and `0` --- `undefined` and `null` #### --answer-- `NaN` and `0` ### --question-- #### --text-- Which of the following is the best name for a boolean variable that checks if a user is allowed to do something on your website? #### --distractors-- `getPermission` --- `handlePermission` --- `permission` #### --answer-- `hasPermission` ### --question-- #### --text-- Which of the following is the best name for a function that runs when a user submits a form? #### --distractors-- `hasSubmitted` --- `formSubmit` --- `didSubmit` #### --answer-- `handleSubmit` ### --question-- #### --text-- What is a sparse array? #### --distractors-- An array where one or more indices have a value of `null`. --- An array where one or more indices have a value of `undefined`. --- An array where one or more indices have a value of an empty object literal. #### --answer-- An array where one or more indices are not assigned a value. ### --question-- #### --text-- In which of the following examples will `arr` NOT be a sparse array? #### --distractors-- ```js const arr = new Array(5); ``` --- ```js const arr = [1, 2, 3]; arr[4] = 4; ``` --- ```js const arr = [1, 2, 3, , 5]; ``` #### --answer-- ```js const arr = Array.from({ length: 5 }); ``` ### --question-- #### --text-- What is the primary purpose of a linter? #### --distractors-- To format code automatically. --- To optimize code for performance. --- To create documentation for code. #### --answer-- To detect potential errors and issues in code. ### --question-- #### --text-- What is a benefit of using a formatter in a codebase? #### --distractors-- They allow developers to compile code more efficiently. --- They convert code to a specific programming language. --- They detect logical errors. #### --answer-- They ensure a consistent code style. ### --question-- #### --text-- In JavaScript, who or what is typically responsible for allocating memory to variables? #### --distractors-- The developer. --- The operating system. --- The server. #### --answer-- The runtime engine. ### --question-- #### --text-- What will be logged to the console in the following code? ```js function trackTotal(initialValue) { let total = initialValue; return function(increment) { total += increment; return total; }; } let track = trackTotal(1); console.log(track(2)); console.log(track(3)); ``` #### --distractors-- ```js 2 5 ``` --- ```js 2 3 ``` --- ```js 5 6 ``` #### --answer-- ```js 3 6 ``` ### --question-- #### --text-- What is hoisting in JavaScript? #### --distractors-- Raising errors to the top of the code. --- The process of creating new variables. --- Automatically moving `var` declarations to the top of the block. #### --answer-- The process of moving variable declarations to the top of their scope. ### --question-- #### --text-- Why is using the `var` keyword considered bad practice in modern JavaScript? #### --distractors-- They're slower than `let` and `const`. --- They cause syntax errors. --- They don't allow type checking. #### --answer-- They're accessible outside their block. ### --question-- #### --text-- What is the purpose of modules in JavaScript? #### --distractors-- To improve code performance. --- To make code more difficult to understand. --- To create new programming languages. #### --answer-- To organize code into reusable units. ### --question-- #### --text-- How do you add an `app.js` script as a module in an HTML document? #### --distractors-- ```html <script type="module/javascript" src="app.js"></script> ``` --- ```html <script src="app.js"></script> ``` --- ```html <script src="app.js" module></script> ``` #### --answer-- ```html <script type="module" src="app.js"></script> ``` ### --question-- #### --text-- Which of the following examples exports the `calculateSum` function from a `utils.js` module and properly imports and uses it in an `app.js` file? #### --distractors-- ```js // utils.js export default function calculateSum(a, b) { return a + b; } // app.js import { calculateSum } from './utils.js'; console.log(calculateSum(2, 3)); ``` --- ```js // utils.js export function calculateSum(a, b) { return a + b; } // app.js import calculateSum from './utils.js'; console.log(calculateSum(2, 3)); ``` --- ```js // utils.js function calculateSum(a, b) { return a + b; } export default calculateSum; // app.js import * as utils from './utils.js'; console.log(utils.calculateSum(2, 3)); ``` #### --answer-- ```js // utils.js export function calculateSum(a, b) { return a + b; } // app.js import { calculateSum } from './utils.js'; console.log(calculateSum(2, 3)); ```