Final Exam Deck #1

Question 1

What is the root prototype?

Answer 1

Object.prototype

Question 2

What is returned for the following statement:
Object.getPrototypeOf( [ ] )

Answer 2

Array.prototype

Question 3

What is returned for the following statement:
Object.getPrototypeOf( )

Answer 3

Object.prototype

Question 4

How/Where are fields declared in a class?

Answer 4

Fields are declared within the constructor method

Question 5

How can we add fields or methods to a class after the class has been created?

Ex: For the class “Car”, add a new field “sound”: “vroom”

Answer 5

We can add fields/methods to the prototype which are accessible by all instantiated object:

Car.prototype.sound = “Vroom”

Question 6

How can we declare private fields within a class?

Answer 6

within the constructor function we do 3 things:

1. use “let” to define a private field
2. getter function
3. setter function

Question 7

What does a subclass inherit from a superclass?

Answer 7

All its public fields and methods

Question 8

Does a subclass inherit a superclass’s private members?

Answer 8

No, a child class does not inherit its parent’s private members

Question 9

How are “extends” and prototypes related?

Answer 9

The “extends” keyword sets a prototype chain where the subclass’s prototype points to the parent class’s prototype

Question 9

If we don’t define a constructor for a subclass what happens?

Answer 9

A default constructor is created where the first line calls the parents constructor using the “super” keyword

Question 9

If we override the default constructor for a subclass what must we always do?

Answer 9

The first line of the constructor must always class the parents constructor using “super(parameter)”

Question 9

Do arrow function have super?

Answer 9

No

Question 10

What is the python equivalent of a JavaScript object?

Answer 10

A dictionary

Question 11

If we try to access an object property that does not exist what happens?

Answer 11

That property gets added to the object

Question 12

What happens when a binding is used without declaration? Ex: x=5

Answer 12

Its automatically added to the “global” object

Question 13

What is the output of the following code? Does it return an error?

x=5
console.log(“Q1: “, x);
console.log(“Q2: “ global.x);

Answer 13

> > 5
5

Question 14

What does “use strict” do?

Answer 14

It prevents all un-declared variables from being added to the “global” object, requiring them to be declared.

Question 15

What is the output of the following code? Does it return an error? If so what is the error?

“use strict”
x=5
console.log(x);
console.log(global.x)

Answer 15

error: x is not defined

Question 16

What is the output of the following code? Does it return an error? If so what is the error?

“use strict”
x=5
console.log(x)
let x;

Answer 16

error: x is not initialized

Question 17

under “use strict”, what happens when we declare a variable with var?

Answer 17

Declarations are hoisted to the top of their scope and and initialized to “undefined”

Question 18

under “use strict”, what happens when we declare a variable with let?

Answer 18

Declarations are hoisted (defined) at their position in the code and initialized to undefined

Question 19

What is the output of the following code? Does it return an error? If so what is the error?

“use strict”
x=5
console.log(x)
var x;

Answer 19

5

Question 20

What is the output of the following code? Does it return an error? If so what is the error?

“use strict”
let x;
x=5
console.log(x)

Answer 20

5

Question 21

What does the following code log?

let values = {
num1: 5,
num2: 7
}

console.log(num3);

values.num3 = 10;
console.log(num3)

Answer 21

> > undefined

> > 10