JavaScript Classes Quiz

To pass the quiz, you must correctly answer at least 18 of the 20 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- What is the purpose of a class in JavaScript? #### --distractors-- To define only properties, not methods. --- To define static variables only. --- To organize only primitive data. #### --answer-- To create reusable blueprints for objects. ### --question-- #### --text-- How do you define a class in JavaScript? #### --distractors-- Using the `className` keyword. --- Using the `object` keyword. --- Using the `constructor` keyword only. #### --answer-- Using the `class` keyword. ### --question-- #### --text-- Which method is used in a class to initialize properties? #### --distractors-- `static` --- `init` --- `define` #### --answer-- `constructor` ### --question-- #### --text-- What does `this` represent inside a class constructor? #### --distractors-- The global class object. --- The function itself. --- An undefined reference. #### --answer-- An instance of the class. ### --question-- #### --text-- Which of the following describes how `this` behaves in an arrow function inside a class method? #### --distractors-- It inherits the value of `this` from the nearest function in a different scope. --- It refers to a newly created instance of the class. --- It inherits the value of `this` from the global object in strict mode. #### --answer-- It inherits the value of `this` from the enclosing scope where it is defined. ### --question-- #### --text-- What is the primary purpose of the `extends` keyword? #### --distractors-- To define static methods in a parent class constructor. --- To create a method in a class. --- To initialize default properties in the parent class. #### --answer-- To create a subclass that inherits from a parent class. ### --question-- #### --text-- Which of the following is an example of how to create a `Car` class that inherits from a `Vehicle` class? #### --distractors-- `class Car uses Vehicle {}` --- `class Car = Vehicle {}` --- `class Car inherits Vehicle {}` #### --answer-- `class Car extends Vehicle {}` ### --question-- #### --text-- What is the output of the following code? ```javascript class Animal { speak() { return "Animal speaks"; } } class Dog extends Animal { speak() { return "Dog barks"; } } const myDog = new Dog(); console.log(myDog.speak()); ``` #### --distractors-- `Animal speaks` --- An error is raised. --- `undefined` #### --answer-- `Dog barks` ### --question-- #### --text-- What is the function of the `super` keyword in a subclass? #### --distractors-- To define a new instance of the parent class. --- To delete methods and properties from the parent class. --- To access only the static methods of the parent class. #### --answer-- To call the constructor or methods of the parent class. ### --question-- #### --text-- Which of the following describes a static method? #### --distractors-- A method that is inaccessible inside the class itself. --- A method that is used only in arrow functions. --- A method that is unique to each instance of a class. #### --answer-- A method that belongs to the class itself, not to any instance. ### --question-- #### --text-- What will the following code output? ```js class Calculator { static add(a, b) { return a + b; } } console.log(Calculator.add(3, 4)); ``` #### --distractors-- An error is raised. --- `undefined` --- `NaN` #### --answer-- `7` ### --question-- #### --text-- How would you access a static property in JavaScript class? #### --distractors-- By using `this.propertyName` within a method. --- By using `instance.propertyName` after creating an instance. --- By using `super.propertyName` within a subclass. #### --answer-- By using `ClassName.propertyName`. ### --question-- #### --text-- In which scenario would you use a static method over an instance method? #### --distractors-- When you need to access and modify the instance's properties. --- When the method needs to be called on an object instance. --- When the method doesn't rely on instance-specific data and operates on class-level data. #### --answer-- When the method operates on data that is shared by all instances of the class. ### --question-- #### --text-- What will the following code output? ```js class MyClass { sayHello() { return "Hello!"; } } console.log(MyClass.sayHello()); ``` #### --distractors-- `Hello!` --- `null` --- `undefined` #### --answer-- It throws an error. ### --question-- #### --text-- What keyword is used to inherit properties and methods from another class? #### --distractors-- `import` --- `inherit` --- `static` #### --answer-- `extends` ### --question-- #### --text-- What is printed by the following code? ```js class Person { static species = "Human"; } console.log(Person.species); ``` #### --distractors-- `undefined` --- `null` --- An error is raised. #### --answer-- `Human` ### --question-- #### --text-- Which of the following best describes inheritance? #### --distractors-- It allows a method to return a new object. --- It allows an instance to define its own properties. --- It allows a static property to be converted into a non-static property. #### --answer-- It allows a class to acquire properties and methods from another class. ### --question-- #### --text-- What happens if a constructor is not defined in a subclass? #### --distractors-- An error will be thrown. --- The subclass will inherit the constructor from any class in the code. --- The subclass cannot create new instances. #### --answer-- The superclass's constructor will be used by default. ### --question-- #### --text-- What does `this` represent in the following code? ```js class Animal { constructor(name) { this.name = name; } } ``` #### --distractors-- The global object. --- The `Animal` class itself. --- An undefined variable. #### --answer-- The instance of `Animal`. ### --question-- #### --text-- What is the primary use of static properties? #### --distractors-- To define default properties for each class instance. --- To override methods in a subclass. --- To define instance-specific data. #### --answer-- To store class-wide data shared across instances.