OOP

Question 1

What is a method?

Answer 1

JavaScript methods are actions that can be performed on objects.

Question 2

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

Answer 2

a method definition is what it will do or can do and how

a method call is it actually doing what its supposed to

Question 3

Describe method definition syntax (structure).

Answer 3

name then colon followed by function and params the opening code block braces then code then closing code block braces

Question 4

Describe method call syntax (structure).

Answer 4

the object name followed by the method and parenthesis and arguments if any

Question 5

How is a method different from any other function?

Answer 5

methods are defined in an object while functions are not

Question 6

What is the defining characteristic of Object-Oriented Programming?

Answer 6

A feature of objects is that an object’s own procedures can access and often modify the data fields of itself (objects have a notion of this or self)
/can contain both data and methods(functionality)

Question 7

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

Answer 7

1. Encapsulation
2. Abstraction
3. Inheritance
4. Polymorphism

Question 8

What is this in JavaScript?

Answer 8

implicit parameter of all JS functions / gives you the lexical scope of whatever it is in

Question 9

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

Answer 9

that 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 10

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

Answer 10

the value of this is determined when the function is called

Question 11

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 11

character

Question 12

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

Answer 12

‘It’s a me Mario! / this refers to character

Question 13

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

Answer 13

‘It’s a me undefined! / this is referring to the window

as hello is whats calling it

Question 14

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

Answer 14

depends on how its called. If its attached to an object then its the object. If not you cant really tell

Question 15

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

Answer 15

Depends if it is attached to an object

Question 16

What kind of inheritance does the JavaScript programming language use?

Answer 16

prototype-based (or prototypal) inheritance.

Question 17

What is a prototype in JavaScript?

Answer 17

a JavaScript prototype is simply an object that contains properties and (predominantly) methods that can be used by other objects.

Question 18

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 18

they are inherited

Question 19

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

Answer 19

in its prototype / looks in its prototype chain

Question 20

What does the new operator do?

Answer 20

creates a new instance of a user defined object

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 21

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

Answer 21

prototype

Question 22

What does the instanceof operator do?

Answer 22

checks if one in item is an instance of another /
The instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object.

Question 23

What is a “callback” function?

Answer 23

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

Question 24

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 24

setTimeout

Question 25

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

Answer 25

SetInterval

Question 26

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

Answer 26

0

Question 27

What do setTimeout() and setInterval() return?

Answer 27

A timeOutID / intervalId