JavaScript

Question 1

What is the event.target?

Answer 1

where the event originated from

Question 2

What is the affect of setting an element to display: none?

Answer 2

removed from the document flow

hides element

Question 3

What does the element.matches() method take as an argument and what does it return?

Question 4

How can you retrieve the value of an element’s attribute?

Answer 4

.getAttribute

Question 5

At what steps of the solution would it be helpful to log things to the console?

Answer 5

every step

Question 6

If you were to add another tab and view to your HTML, but you didn’t use event delegation, how would your JavaScript code be written instead?

Answer 6

create separate event listeners for every tab

Question 7

If you didn’t use a loop to conditionally show or hide the views in the page, how would your JavaScript code be written instead?

Answer 7

create conditional block for each view

Question 8

What is JSON?

Answer 8

text based data format for representing data based on JavaScript object syntax

Question 9

What are serialization and deserialization?

Answer 9

process of converting an object into a stream of bytes to more easily save or transmit

constructing a data structure or object from a series of bytes

Question 10

Why are serialization and deserialization useful?

Answer 10

makes it easier to save or transmit data

Question 11

How do you serialize a data structure into a JSON string using JavaScript?

Answer 11

JSON.stringify() method

Question 12

How do you deserialize a JSON string into a data structure using JavaScript?

Answer 12

JSON.parse() method

Question 13

How do you store data in localStorage?

Answer 13

.setItem() method
(key name, value)

Question 14

How do you retrieve data from localStorage?

Answer 14

.getItem() method
(key/property name)

Question 15

What data type can localStorage save in the browser?

Answer 15

string data type

Question 16

When does the ‘beforeunload’ event fire on the window object?

Answer 16

when user refreshes or exit window

Question 17

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

Question 18

Describe method definition syntax (structure).

Question 19

Describe method call syntax (structure).

Question 20

How is a method different from any other function?

Question 21

What is the defining characteristic of Object-Oriented Programming?

Answer 21

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

Question 22

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

Answer 22

abstraction, encapsulation, inheritance, polymorphism

Question 23

What is “abstraction”?

Answer 23

being able to work complex things in simple ways

Question 24

What does API stand for?

Answer 24

application programming interface

Question 25

What is the purpose of an API?

Answer 25

to enable applications to exchange data and functionality easily and securely

Question 26

What is this in JavaScript?

Answer 26

refers to an object that is executing the current piece of code

Question 27

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

Answer 27

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

Question 28

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

Answer 28

call time

Question 29

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 29

character object

Question 30

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

Answer 30

It’s-a-me, Mario!

theres an object to the left of the function(method) being called

Question 31

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

Answer 31

It’s-a-me, undefined!

no object before function call

Question 32

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

Answer 32

you can’t, no way to know, waiting to be used

Question 33

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

Answer 33

object before the function(method) being called

Question 34

What kind of inheritance does the JavaScript programming language use?

Answer 34

prototype-based (prototypal)

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

Question 35

What is a prototype in JavaScript?

Answer 35

an object with shared behavior or data that can be stored in one place and shared with all created instances

the procedure in which JavaScript objects inherit features from one another

Question 36

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 36

“borrow” methods from prototype object

Question 37

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

Answer 37

each prototype object

Question 38

What does the new operator do?

Answer 38

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

1. created a blank, plain JavaScript object
2. takes the value of the prototype property off the function being run with the new operator and make it a property of the new object
3. makes new object this
4. if nothing was returned(normally nothing is returned), the object created gets returned

Question 39

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

Answer 39

prototype

Question 40

What does the instanceof operator do?

Answer 40

tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object, return value is a boolean

(object instanceof constructor)

Question 41

What is a “callback” function?

Answer 41

function passed into another function as an argument

Question 42

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 42

setTimeout()

Question 43

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

Answer 43

setInterval

Question 44

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

Answer 44

0

Question 45

What do setTimeout() and setInterval() return?

Answer 45

positive integer value which identifies the timer created