DOM

Question 1

Why do we log things to the console?

Answer 1

for debugging or to know what you are working with

Question 2

What is a “model”?

Answer 2

a representation or recreation of something that isn’t exact

Question 3

Which “document” is being referred to in the phrase Document Object Model?

Answer 3

the html document

Question 4

What is the word “object” referring to in the phrase Document Object Model?

Answer 4

data type object

Question 5

What is a DOM Tree?

Answer 5

any element and holds all the configuration and the sum of all its parts

Question 6

Give two examples of document methods that retrieve a single element from the DOM.

Answer 6

getElementId(), querySelector()

Question 7

Give one example of a document method that retrieves multiple elements from the DOM at once.

Answer 7

document.querySelectorAll()

Question 8

Why might you want to assign the return value of a DOM query to a variable?

Answer 8

to use the variable and not calling the query function every time you need to use it

Question 9

What console method allows you to inspect the properties of a DOM element object?

Answer 9

console.dir() or dir method

Question 10

Why would a

 tag need to be placed at the bottom of the HTML content instead of at the top?

Answer 10

to load all the content

Question 11

What does document.querySelector() take as its argument and what does it return?

Answer 11

it takes a string element with css selector and matches it

Question 12

What does document.querySelectorAll() take as its argument and what does it return?

Answer 12

it takes a string element with css selector and node lists (collection of nodes)

Question 13

Why do we log things to the console?

Answer 13

to debug and to know what you are working with

Question 14

What is the purpose of events and event handling?

Answer 14

something occurred and information gets sent out also for allowing users to interact with the web page

Question 15

Are all possible parameters required to use a JavaScript method or function?

Answer 15

no

Question 16

What method of element objects lets you set up a function to be called when a specific type of event occurs?

Answer 16

addEventListener(), has 2 argument the string containing the event and the second argument is the callback function

Question 17

What is a callback function?

Answer 17

when you pass a function as a value to another function

Question 18

What object is passed into an event listener callback when the event fires?

Answer 18

an object with a huge list of properties to describe the event that just occurred

Question 19

What is the event.target? If you weren’t sure, how would you check? Where could you get more information about it?

Answer 19

the element where the event occurred. log it out or mdn.

Question 20

What is the difference between these two snippets of code?
element.addEventListener(‘click’, handleClick)
element.addEventListener(‘click’, handleClick())

Answer 20

the first one calls the function as a call back, while the second one calls the function immediately and nothing gets returned

Question 21

What is the className property of element objects?

Answer 21

the value of the class attribute (not a selector)

Question 22

How do you update the CSS class attribute of an element using JavaScript?

Answer 22

setAttribute() method

Question 23

What is the textContent property of element objects?

Answer 23

element . textContent

Question 24

How do you update the text within an element using JavaScript?

Answer 24

element name with dot notation textContent “=” new string or variable

Question 25

Is the event parameter of an event listener callback always useful?

Answer 25

no, but most of the time it will be

Question 26

Would this assignment be simpler or more complicated if we didn’t use a variable to keep track of the number of clicks?

Answer 26

more complicated cause then you would have to code each “click”

Question 27

Why is storing information about a program in variables better than only storing it in the DOM?

Answer 27

then you can use the variable instead of querying the dom element everytime

Question 28

What event is fired when a user places their cursor in a form control?

Answer 28

focus()

Question 29

What event is fired when a user’s cursor leaves a form control?

Answer 29

blur()

Question 30

What event is fired as a user changes the value of a form control?

Answer 30

input

Question 31

What event is fired when a user clicks the “submit” button within a <form>?

Answer 31

submit event fires on the form element itself only

Question 32

What does the event.preventDefault() method do?

Answer 32

prevents default behavior

Question 33

What does submitting a form without event.preventDefault() do?

Answer 33

it allows the page to refresh and to submit the data to the same page

Question 34

What property of a form element object contains all of the form’s controls.

Answer 34

form.elements or the elements property

Question 35

What property of a form control object gets and sets its value?

Answer 35

the value property

Question 36

What is one risk of writing a lot of code without checking to see if it works so far?

Answer 36

you wont know what part is working or not working

Question 37

What is an advantage of having your console open when writing a JavaScript program?

Answer 37

you can see if there is an error

Question 38

Does the document.createElement() method insert a new element into the page?

Answer 38

No

Question 39

How do you add an element as a child to another element?

Answer 39

appendChild() method

Question 40

What do you pass as the arguments to the element.setAttribute() method?

Answer 40

(name of the attribute in a string, new value)

Question 41

What steps do you need to take in order to insert a new element into the page?

Answer 41

createElement() -> make configurations (add text and class)-> querySelect for parent ->
parent.appendChild().

Question 42

What is the textContent property of an element object for?

Answer 42

text content

Question 43

Name two ways to set the class attribute of a DOM element.

Answer 43

className or setAttribute()

Question 44

What are two advantages of defining a function to create something (like the work of creating a DOM tree)?

Answer 44

you dont have to create a dom tree over and over again as well as gives reusability

Question 45

What is the event.target?

Answer 45

the element that was clicked on or interacted with

Question 46

Why is it possible to listen for events on one element that actually happen its descendent elements?

Answer 46

event bubbling to the top

Question 47

What DOM element property tells you what type of element it is?

Answer 47

tag name property value all uppercase

Question 48

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

Answer 48

takes css selector as argument and returns the nearest parent element that matches with the css selector

Question 49

How can you remove an element from the DOM?

Answer 49

element.remove()

Question 50

If you wanted to insert new clickable DOM elements into the page using JavaScript, how could you avoid adding an event listener to every new element individually?