Object Oriented Programming (OOP)

Question 1

What is a method?

Answer 1

a function stored in the property of an object

Question 2

How can you tell the difference between method definitions and method calls?

Answer 2

method definition will always have the function keyword and a code block.
method call is always attached to an object.

Question 3

Describe method call syntax:

Answer 3

object.method( )

Question 4

How is a method different from any other function?

Answer 4

a method is a property of an object

Question 5

What is the defining characteristic of object-oriented-programming (OOP)?

Answer 5

objects can contain both data and behavior(methods)

Question 6

What are the four principles of object-oriented-programming?

Answer 6

Abstraction, Encapsulation, Inheritance, Polymorphism

Question 7

What is “abstraction”?

Answer 7

being able to work with complex things in simple ways

Question 8

What does API stand for?

Answer 8

Application Programming Interface

Question 9

What is the purpose of an API?

Answer 9

communication between two softwares

Question 10

What is this in JavaScript?

Answer 10

an implicit parameter of all JavaScript functions - the object that we’re working in

Question 11

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

Answer 11

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

Question 12

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

Answer 12

call time - this does not exist/have value until the function is called

Question 13

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

Answer 13

you cant - if a function is just being defined, this does not exist yet

Question 14

How can you tell what the value of this is for a particular function or method call 👀?

Answer 14

check the object to the left of the dot

Question 15

What kind of inheritance does the JavaScript programming language use?

Answer 15

prototype-based inheritance (prototypal inheritance)

Question 16

What is a prototype in JavaScript?

Answer 16

an object that contains properties and (predominantly) methods that can be used by other objects

Question 17

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

Answer 17

via inheritance from the prototype

Question 18

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

Answer 18

inside the prototype object linked to the object. it goes up the prototype chain until it finds what it needs

Question 19

What does the new operator do?

Answer 19

• creates a blank, plain JavaScript object.
• adds a property to the new object (__proto__) that links to the constructor function’s prototype object.
• binds the newly created object instance as the this context (all references to this in the constructor function now refer to the object created in first step)
• returns this

Question 20

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

Answer 20

the prototype property

Question 21

What does the instanceof operator do?

Answer 21

• tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. The return value is a boolean value.
• an instance is a created example of a thing
• example :

function Car(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;
}
const auto = new Car('Honda', 'Accord', 1998);

console.log(auto instanceof Car);
// expected output: true

Question 22

What is a ‘callback’ function?

Answer 22

a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine/action.

Question 23

Besides adding an eventListener callback function to an element or document, what is one way to delay the execution of a JavaScript function until some point in the future?

Answer 23

the setTimeout( ) global function

Question 24

How can you set up a function to be called repeatedly without using a loop?

Answer 24

setInterval( )

Question 25

What is the default time delay if you omit (leave out) the delay parameter from setTimeout( ) or setInterval( )?

Answer 25

0

Question 26

What do setTimeout( ) and setInterval( ) return?

Answer 26

a timeoutId