OOP

Question 1

What is a method?

Answer 1

A method is a function which is a property of an object.

Question 2

How can you tell the difference between a method definition and a method call?

Answer 2

method definition is writing out the function inside object and The call() method calls a function with a given this value and arguments provided individually

Question 3

Describe method definition syntax (structure).

Answer 3

function name, colon, function key word, optional parameter, opening curly brace, code block, closing curly brace, comma.

Question 4

How is a method different from any other function?

Answer 4

The difference is that a method is associated with an object, while a function is not

Question 5

What is the defining characteristic of Object-Oriented Programming?

Answer 5

Object Oriented programming (OOP) is a programming paradigm that relies on the concept of classes and objects. It is used to structure a software program into simple, reusable pieces of code blueprints (usually called classes), which are used to create individual instances of objects. Encapsulation.

Question 6

What are the four “principles” of Object-Oriented Programming?

Answer 6

Abstraction, Encapsulation, Inheritance, Polymorphism

Question 7

What is “abstraction”?

Answer 7

Through the process of abstraction, a programmer hides all but the relevant data about an object in order to reduce complexity and increase efficiency.

Question 8

What does API stand for?

Answer 8

Application Programming Interface

Question 9

What is the purpose of an API?

Answer 9

software intermediary that allows two applications to talk to each other

Question 10

what is method call syntax?

Answer 10

object name.method(arguments)

Question 11

What is this in JavaScript?

Answer 11

The JavaScript this keyword refers to the object it belongs to

Question 12

What does it mean to say that this is an “implicit parameter”?

Answer 12

it is available in a function’s code block even though it was never included in the function’s parameter list or declared

Question 13

When is the value of this determined in a function; call time or definition time?

Answer 13

the value of this is determined at call time.

Question 14

Given the above character object, what is the result of the following code snippet? Why?

Answer 14

It’s a me Mario!

because this.firstName = firstName of character object

Question 15

Given the above character object, what is the result of the following code snippet? Why?

Answer 15

“It’s-a-me Mario!”

because this.firstName = firstName of character object

Question 16

Given the above character object, what is the result of the following code snippet? Why?
var hello = character.greet;
hello();

Answer 16

“It’s-a-me, undefined!”

because variable hello is being defined outside of the character object; this no longer points to the character object.

Question 17

How can you tell what the value of this will be for a particular function or method definition?

Answer 17

the value of this is determined when the function is called, not when it is defined.

Question 18

What kind of inheritance does the JavaScript programming language use?

Answer 18

prototype-based (prototypal) inheritance

Question 19

What is a prototype in JavaScript?

Answer 19

The prototype is an object that is associated with every functions and objects by default in JavaScript

Question 20

What is a prototype in JavaScript?

Answer 20

The prototype is an object that is associated with every functions and objects by default in JavaScript

Question 21

How is it possible to call methods on strings, arrays, and numbers even though those methods don’t actually exist on objects, arrays, and numbers?

Answer 21

methods are defined on a prototype object and arrays, strings and numbers borrow the methods when needed. prototypal inheritance.

Question 22

If an object does not have it’s own property or method by a given key, where does JavaScript look for it?

Answer 22

the object’s prototype.

Question 23

What does the new operator do?

Answer 23

new operator is used to create an instance of a user-defined object type or one of built in object types which have a constructor function.
The new keyword does the following things:

1. Creates a blank, plain JavaScript object.
2. Adds a property to the new object (__proto__) that links to the constructor function’s prototype object
3. Binds the newly created object instance as the this context (i.e. all references to this in the constructor function now refer to the object created in the first step).
4. Returns this if the function doesn’t return an object.

Question 24

What property of JavaScript functions can store shared behavior for instances created with new?

Answer 24

prototype property