OOP (Object Oriented Programming)

Question 1

What is a method?

Answer 1

A function stored in a property of an object

Question 2

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

Answer 2

o Method definitions will always have a function keyword and a code block
o Method calls start with an object name and has arguments that are being passed

Question 3

Describe method definition syntax (structure).

Answer 3

propertyName: functionName( ) {
Return ‘anything’;
}

Question 4

Describe method call syntax (structure).

Answer 4

objectName.method( )

Question 5

How is a method different from any other function?

Answer 5

They are functions stored in an object

Question 6

What is the defining characteristic of Object-Oriented Programming?

Answer 6

Objects can contain both:

   - Data (as properties)
   - Behavior (as methods)

Question 7

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

Answer 7

o Abstraction
o Encapsulation
o Inheritance
o Polymorphism

Question 8

What is “abstraction”?

Answer 8

Being able to work with (possibly) complex things in simple ways (such as, turning a light on/off)

Question 9

What does API stand for?

Answer 9

Application Programming Interface

Question 10

What is the purpose of an API?

Answer 10

Give programmers a way to interact with a system(s) in a simplified, consistent fashion (aka abstraction) without knowing about how they all work independenly.

Question 11

What is ‘this’ in JavaScript?

Answer 11

The object that you’re working within

Question 12

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

Answer 12

The parameter is available (in a function’s code block) even though it was never included in the function’s parameter list OR declared in a var

Question 13

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

Answer 13

Call time

Question 14

What does ‘this’ refer to in the following code snippet?

var character = {
  firstName: 'Mario',
  greet: function () {
    var message = 'It\'s-a-me, ' + this.firstName + '!';
    console.log(message);
  }
};

Answer 14

Undefined (there is nothing in front of greet)

Question 15

Given this character object:

var character = {
  firstName: 'Mario',
  greet: function () {
    var message = 'It\'s-a-me, ' + this.firstName + '!';
    console.log(message);
  }
};

What is the result of the following code snippet? Why?
character.greet();

Answer 15

It’s a me, Mario! Because greet is being called on the character object

Question 16

Given this character object:

var character = {
  firstName: 'Mario',
  greet: function () {
    var message = 'It\'s-a-me, ' + this.firstName + '!';
    console.log(message);
  }
};

What is the result of the following code snippet? Why?
var hello = character.greet;
hello();

Answer 16

It’s a me, undefined!

Because ‘this’ is being called from the window object and not 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

There is no way to know in a definition because there is no value yet

Question 18

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

Answer 18

By checking the object left of the dot

Question 19

What kind of inheritance does the JavaScript programming language use?

Answer 19

Prototype-based (prototypal) inheritance

Question 20

What is a prototype in JavaScript?

Answer 20

Object with properties and methods that can be reused

Question 21

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 21

Via inheritance from the prototypes (prototypal inheritance)

Question 22

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

Answer 22

its prototype (starts from the nearest prototype and moves up until it finds what it needs)

Question 23

What does the ‘new’ operator do?

Answer 23

Let you create an instance of a user-defined or built-in object type that has a constructor function (create a function that generates objects for you).

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

Question 25

What does the instanceof operator do?

Answer 25

Tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object and returns a Boolean value

Question 26

What is a “callback” function?

Answer 26

A function passed into another function as an argument

Question 27

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

Answer 27

setTimeOut()

Question 28

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

Answer 28

setInterval()

Question 29

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

Answer 29

0 (it will execute as soon as all the other codes finish running)

Question 30

What do setTimeout() and setInterval() return?

Answer 30

timeoutID
(you always want to set your var countdownId = setInterval( variable, time) so when you declare your clearInterval(), you can pass your countdownId so it stops the process when you need it to instead of running forever)