JavaScript Object-Oriented Programming: Master Classes, Objects, and Inheritance

Question 1

In JavaScript, which syntax correctly extends the built-in Error class?

Accepted Answer

class MyError extends Error { }

Answer

prototype MyError = extend Error { }

Answer

MyError := Error.prototype { }

Answer

MyError inheritsfrom Error { }

Question 2

In JavaScript, what does the 'this' keyword represent?

Accepted Answer

The current object

Answer

The global object

Answer

The parent object

Answer

The window object

Question 3

Which of the following is NOT a characteristic of object-oriented programming in JavaScript?

Accepted Answer

Sequential Execution

Answer

Encapsulation

Answer

Modularity

Answer

Inheritance

Question 4

In JavaScript, what does the 'this' keyword within a method refer to?

Accepted Answer

The object that owns the method

Answer

The global object

Answer

The object that called the method

Answer

The parent object

Question 5

What is the purpose of the 'extends' keyword in JavaScript?

Accepted Answer

To define a derived class

Answer

To define a base class

Answer

To define a method

Answer

To define a variable

Question 6

What is the difference between a 'getter' and a 'setter' method?

Accepted Answer

Getters retrieve values, setters set values

Answer

Setters retrieve values, getters set values

Answer

Both methods set values

Answer

Both methods retrieve values

Question 7

What is the purpose of the 'super' keyword in JavaScript?

Accepted Answer

To access parent class properties and methods

Answer

To access child class properties and methods

Answer

To define a default constructor

Answer

To create a new object

Question 8

What is the concept of 'encapsulation' in object-oriented programming?

Accepted Answer

Hiding implementation details from the user

Answer

Exposing implementation details to the user

Answer

Combining data and methods in one unit

Answer

Restricting access to certain object properties

Question 9

In JavaScript, what reserved word is used to define a class?

Accepted Answer

class

Answer

object

Answer

new

Answer

prototype

Question 10

What is the role of the 'this' keyword in JavaScript object-oriented programming?

Accepted Answer

References the current object

Answer

Creates a new object

Answer

Accesses static methods

Answer

Calls the constructor

Question 11

In JavaScript, what is the correct syntax to create an object instance from a class?

Accepted Answer

let objectName = new ClassName()

Answer

let objectName = ClassName()

Answer

let objectName : ClassName()

Answer

let new objectName = ClassName()

Question 12

Which of the following is NOT an advantage of inheritance in JavaScript?

Accepted Answer

Increased memory consumption

Answer

Code reusability

Answer

Reduced complexity

Answer

Improved maintainability

Question 13

What is the primary purpose of a constructor in JavaScript object-oriented programming?

Accepted Answer

Initialize object properties

Answer

Define class methods

Answer

Create new objects

Answer

Specify the class prototype

Question 14

Which method is used to access static methods in a JavaScript class?

Accepted Answer

ClassName.methodName()

Answer

objectName.methodName()

Answer

this.methodName()

Answer

methodName()

Question 15

Explain the difference between the 'extends' and 'implements' keywords in JavaScript OOP.

Accepted Answer

'extends' creates a subclass, while 'implements' creates an interface

Answer

'implements' creates a subclass, while 'extends' creates an interface

Answer

Both 'extends' and 'implements' create subclasses

Answer

Both 'extends' and 'implements' create interfaces

Question 16

What is the proper way to define a property within a JavaScript class?

Accepted Answer

this.propertyName = value

Answer

propertyName = value

Answer

property: value

Answer

let propertyName = value

Question 17

What is the purpose of the 'super' keyword in JavaScript OOP?

Accepted Answer

Calls the parent class constructor

Answer

Accesses parent class methods

Answer

Creates a new object

Answer

Defines static methods

Question 18

What is the primary purpose of a constructor method in a JavaScript class?

Accepted Answer

To initialize an object's properties

Answer

To define an object's methods

Answer

To create a new instance of the class

Answer

To set the prototype of the class

Question 19

Which syntax is valid for defining a class in JavaScript?

Accepted Answer

class MyClass {}

Answer

var MyClass = class {}

Answer

function MyClass() {}

Answer

MyClass = class {}

Question 20

What is the key distinction between a method and a property in JavaScript OOP?

Accepted Answer

Methods modify the object, while properties do not

Answer

Properties modify the object, while methods do not

Answer

Methods are inherited, while properties are not

Answer

Properties are inherited, while methods are not

Question 21

Which syntax correctly inherits from the `Animal` class in JavaScript?

Accepted Answer

class Dog extends Animal {}

Answer

var Dog = extends Animal {}

Answer

function Dog extends Animal {}

Answer

Dog extends Animal = class {}

Question 22

What is the primary role of the `super` keyword in JavaScript OOP inheritance?

Accepted Answer

To call the constructor of the parent class

Answer

To access the properties of the parent class

Answer

To modify the prototype of the child class

Answer

To define the methods of the child class

Question 23

What is the difference between a static method and an instance method in JavaScript OOP?

Accepted Answer

Static methods are called on the class, while instance methods are called on an instance of the class

Answer

Instance methods are called on the class, while static methods are called on an instance of the class

Answer

Static methods modify the object, while instance methods modify the class

Answer

Instance methods modify the object, while static methods modify the class

Question 24

Which syntax correctly defines a static method in JavaScript?

Accepted Answer

MyClass.staticMethod()

Answer

var MyClass.staticMethod = function() {}

Answer

function MyClass.staticMethod() {}

Answer

static MyClass.staticMethod()

Question 25

What is the purpose of the `this` keyword in JavaScript OOP methods?

Accepted Answer

To refer to the current object

Answer

To access the class of the current object

Answer

To modify the prototype of the current object

Answer

To define the methods of the current object

Question 26

How does the 'bind' method in JavaScript create a new function with a specific 'this' value?

Accepted Answer

Returns a new function that executes the original function with the specified 'this' value.

Answer

Modifies the original function to have the specified 'this' value.

Answer

Enables calling a function with a different number of arguments.

Answer

Creates a new object that inherits from the original function.

Question 27

How do you create a child object that inherits properties and methods from a parent object using prototype-based inheritance in JavaScript?

Accepted Answer

Set the prototype of the child object to the parent object using Object.setPrototypeOf().

Answer

Define a new function with the same name as the parent object and set its prototype to the parent object.

Answer

Use the extends keyword to create a child class that inherits from the parent class.

Answer

Assign the properties and methods of the parent object directly to the child object.

Question 28

In JavaScript, what's the key difference between using the 'class' keyword and the 'function' keyword when creating a class?

Accepted Answer

The 'class' keyword defines a blueprint for objects, while the 'function' keyword creates an object instance.

Answer

The 'function' keyword allows for parameterization, unlike the 'class' keyword.

Answer

The 'class' keyword is used solely for inheritance, while the 'function' keyword cannot be used for inheritance.

Answer

The 'function' keyword creates a private scope, while the 'class' keyword creates a public scope.

Question 29

Delineate the correct syntax to establish a class in JavaScript?

Accepted Answer

class ClassName { }

Answer

ClassName = class { }

Answer

{ ClassName }

Answer

create class ClassName { }

Question 30

Describe the purpose of the 'this' keyword within the context of JavaScript object-oriented programming?

Accepted Answer

To reference the current object

Answer

To reference the parent object

Answer

To reference the child object

Answer

To reference the global object

Question 31

Which of the following options accurately describes a key benefit of utilizing inheritance in JavaScript?

Accepted Answer

All of the aforementioned

Answer

Code reusability

Answer

Enhanced maintainability

Answer

Reduced complexity

Question 32

In JavaScript, which syntax correctly defines a class?

Accepted Answer

class Person { ... }

Answer

Person class { ... }

Answer

const Person = { ... }

Answer

function Person() { ... }

Question 33

Which keyword in JavaScript is used to create an object based on a class?

Accepted Answer

new

Answer

init

Answer

create

Answer

make

Question 34

To access an object property in JavaScript, which syntax is correct?

Accepted Answer

.propertyName

Answer

[propertyName]

Answer

propertyName

Answer

get propertyName()

Question 35

In JavaScript, what is the distinction between a class and an object?

Accepted Answer

A class is a blueprint, while an object is an instance of that blueprint

Answer

An object is a blueprint, while a class is an instance of that blueprint

Answer

Classes and objects are interchangeable concepts

Answer

Objects can only be created from primitive data types

Question 36

In JavaScript, what role does the 'this' keyword serve?

Accepted Answer

References the current object

Answer

Provides access to global variables

Answer

Attaches a function to a particular object

Answer

Creates a new instance of a class

Question 37

Which of the following is NOT a fundamental principle of object-oriented programming?

Accepted Answer

Concurrency

Answer

Encapsulation

Answer

Abstraction

Answer

Inheritance

Question 38

What is the primary purpose of a constructor method in a JavaScript class?

Accepted Answer

To initialize the object's properties and state

Answer

To define the object's behavior and methods

Answer

To inherit properties from a parent class

Answer

To create new instances of the class

Question 39

Which of the following is a valid syntax for creating an object in JavaScript?

Accepted Answer

let object = new ClassName();

Answer

let object = ClassName.create();

Answer

let object = new Object();

Answer

let object = ClassName();

Question 40

What key distinction exists between a class and an object in JavaScript?

Accepted Answer

A class is a template for creating objects, while an object is a specific instance of a class.

Answer

A class is an object, while an object is a property of a class.

Answer

A class is a function, while an object is the value returned by that function.

Answer

There is no fundamental difference between a class and an object in JavaScript.

Question 41

In JavaScript, which keyword is used to inherit properties and methods from a parent class?

Accepted Answer

extends

Answer

inherits

Answer

prototype

Answer

super

Question 42

What is the primary benefit of encapsulation in object-oriented programming?

Accepted Answer

It promotes data hiding and protection from unauthorized access.

Answer

It enhances code reusability and maintainability.

Answer

It improves performance by optimizing memory usage.

Answer

It simplifies debugging and error handling.

Question 43

What is the function of a getter method in JavaScript?

Accepted Answer

To retrieve the value of a private property

Answer

To modify the value of a private property

Answer

To invoke a function associated with a property

Answer

To create a new instance of a class

Question 44

Which syntax correctly defines a private property using ES6?

Accepted Answer

private privateProperty = Symbol();

Answer

let _privateProperty;

Answer

const #privateProperty;

Answer

var privateProperty = Symbol();

Question 45

Within a JavaScript method, what is the primary purpose of the 'this' keyword?

Accepted Answer

To refer to the current object the method belongs to

Answer

To refer to the parent object of the current object

Answer

To refer to the global object

Answer

To refer to the function object itself

Question 46

In JavaScript object-oriented programming, which method is most effective for handling errors?

Accepted Answer

Using 'try-catch-finally' blocks

Answer

Using only the 'try' block

Answer

Using the 'catch' block without a preceding 'try' block

Answer

Using 'try-catch' blocks without a 'finally' block

Question 47

In JavaScript, what is the primary difference between abstract and regular classes?

Accepted Answer

Abstract classes cannot be directly created into objects, unlike regular classes.

Answer

Regular classes can include abstract methods, but abstract classes cannot.

Answer

Abstract classes can inherit from regular classes, but not the other way around.

Question 48

What is the key purpose of a constructor method within a JavaScript class?

Accepted Answer

Initialize object properties

Answer

Define class methods

Answer

Inherit from parent classes

Question 49

Which syntax is correct for creating a new instance of a JavaScript class?

Accepted Answer

const myObject = new ClassName();

Answer

const myObject = ClassName.new();

Answer

const myObject = ClassName();

Answer

const myObject = create(ClassName);

Question 50

What is the primary function of the `this` keyword in JavaScript OOP?

Accepted Answer

References the current object

Answer

Defines the class constructor

Answer

Accesses static class members

Answer

Inherits properties from parent classes

Question 51

Which key benefit does inheritance offer in OOP?

Accepted Answer

Code reusability and maintenance

Answer

Enhanced security

Answer

Reduced memory overhead

Answer

Improved performance

Question 52

Explain the fundamental difference between a class and an object in JavaScript OOP.

Accepted Answer

A class is a blueprint, while an object is an instance of that blueprint

Answer

There is no difference

Answer

A class has methods, while an object has properties

Answer

A class is static, while an object is dynamic

Question 53

What is the primary purpose of the `super` keyword in JavaScript OOP?

Accepted Answer

Calls the constructor of the parent class

Answer

Overrides methods from the parent class

Answer

Defines static class members

Answer

Inherits properties from the parent class

Question 54

What is the role of a prototype in JavaScript OOP?

Accepted Answer

Provides shared properties and methods to objects

Answer

Inherits properties from parent classes

Answer

Defines the class constructor

Answer

Handles object events