OOP

Question 1

What is a method?

Answer 1

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: declaring/defining. code is there but nothing happens

method call: DOT NOTATION
call the function to run the code

Question 3

Describe method definition syntax (structure).

Answer 3

var objectName = {
methodName: function(parameters) {
code
return result
};

Question 4

Describe method call syntax (structure).

Answer 4

ObjectName.methodName(parameters);

Question 5

How is a method different from any other function?

Answer 5

it is the property of an object

Question 6

IMPORTANT!

What is the defining characteristic of Object-Oriented Programming?

Answer 6

objects can contain both data (as properties) and behavior (as methods)

Question 7

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

Answer 7

Abstraction
Encapsulation
Inheritance
Polymorphism

Question 8

What is “abstraction”?

Answer 8

being able to work with (possibly) complex things in simple ways.

ex/ light switch

ex/ car automatic transmission

Question 9

What does API stand for?

Answer 9

application programming interface

Question 10

What is the purpose of an API?

Answer 10

NUTSHELL: allows apps to disseminate or receive information between each other. interacting with an application to get or send info.

SIMPLE DEFINITION: an API delivers a user response to a system and sends the system’s response back to a user.

COMPLEX DEFITION: it is a set of functions that allows applications to access data and interact with external software components, operating systems, or microservices.

Question 11

What is “this” in JavaScript?

Answer 11

reference to the lexical scope of the function at call time

Question 12

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

Answer 12

“this” parameter does not need to be explicitly defined

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

character

Question 15

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

Answer 15

you can’t know for sure until it is called

Question 16

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

Answer 16

look left of the dot

that is typically the calling object

Question 17

What kind of inheritance does the JavaScript programming language use?

Answer 17

prototype-based (or prototypal) inheritance.

JavaScript objects give certain behaviors (methods) or data (properties) to other objects.

Question 18

What is a prototype in JavaScript?

Answer 18

an object with functionality that will be inherited down to any object connected to that prototype

original model on which something is patterned

Question 19

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 19

You can set prototypes

Question 20

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

Answer 20

[[prototype]] chain

Question 21

IMPORTANT

What does the “new” operator do?

Answer 21

create an instance of a user-defined object type or of one of the built-in object types that has a constructor function.

1. creates blank object
2. adds property/fxns to new object __proto__to link to fxn’s prototype object
3. binds newly created object to “this” (“this” now referes to object created in step 1)
4. returns “this” if fxn doesnt return an object. no need to put in “return” keyword

Question 22

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

Answer 22

.prototype property

Question 23

What does the instanceof operator do?

Answer 23

SIMPLE: checks to see if variable was created from a specific constructor

COMPLEX: tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object.

returns boolean

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

set timeout

Question 25

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

Answer 25

set interval

Question 26

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

Answer 26

1 second

Question 27

What do setTimeout() and setInterval() return?

Answer 27

setTimeout - returns positive integer

Interval - numeric nonzero value that identifies the timer

Question 28

What is AJAX?

Answer 28

Asynchronous JavaScript And XML

AJAX is a tool for making network requests within website without needing to load a new webpage

uses XML to request data and JS to display user data

Question 29

Which object is built into the browser for making HTTP requests in JavaScript?

Answer 29

xhr

XMLHttpRequest

Question 30

What event is fired by XMLHttpRequest objects when they are finished loading the data from the server?

Answer 30

‘load’ event

WE CARE ABOUT ‘load’ & ‘error’

other events fired by xhr objects 
('progress' - update progress 
'load' - transfer complete
'error - transfer failed' 
'abort' - if client canceled)

Question 31

An XMLHttpRequest object has an addEventListener() method just like DOM elements.

How is it possible that they both share this functionality?

Answer 31

prototype chain:

event target (least specific) < event target xhr < xhr (most specific)

event target < node < DOM element