DOM

Question 1

Why do we log things to the console?

Answer 1

to verify and check code

Question 2

What is a “model”?

Answer 2

a representation of something

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

Question 5

What is a DOM Tree?

Answer 5

an element plus its content and configuration

Question 6

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

Answer 6

querySelector and getElementbyId

Question 7

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

Answer 7

querySelectorAll

Question 8

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

Answer 8

If you want to use the same DOM element more than once

Question 9

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

Answer 9

console.dir

Question 10

Why would a

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

Answer 10

it needs to load all the elements

Question 11

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

Answer 11

it takes strings as an argument and returns the first element that matches

Question 12

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

Answer 12

it takes a string as an argument and returns a nodelist

Question 13

What is the purpose of events and event handling?

Answer 13

it allows the developer to make changes when the user does something

Question 14

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

Answer 14

no

Question 15

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

Answer 15

addEventListener

Question 16

What is a callback function?

Answer 16

taking a function definition and passing it down

Question 17

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

Answer 17

target

Question 18

What is the event.target?

Answer 18

the element where the event originated on

Question 19

What is the className property of element objects?

Answer 19

it holds the value of the class name property in an html document

Question 20

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

Answer 20

elementName.className = newClassName

Question 21

What is the textContent property of element objects?

Answer 21

it holds all the text that the element includes

Question 22

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

Answer 22

elementName.textContent = newText

Question 23

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

Answer 23

no

Question 24

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

Answer 24

focus

Question 25

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

Answer 25

blur

Question 26

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

Answer 26

input

Question 27

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

Answer 27

submit

Question 28

What does the event.preventDefault() method do?

Answer 28

Prevents the default action

Question 29

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

Answer 29

it reloads the page

Question 30

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

Answer 30

the elements property

Question 31

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

Answer 31

the form method

Question 32

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

Answer 32

No

Question 33

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

Answer 33

Append Child

Question 34

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

Answer 34

the name of the attribute and value

Question 35

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

Answer 35

Create element, query an element on the html document then appendChild the new element to the html element

Question 36

What is the textContent property of an element object for?

Answer 36

to set or get the text value of an element

Question 37

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

Answer 37

setAttribute, className

Question 38

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

Answer 38

you can use it more than once and its easily callable

Question 39

What is the event.target?

Answer 39

where the event started

Question 40

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

Answer 40

due to event bubbling

Question 41

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

Answer 41

tagName.property

Question 42

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

Answer 42

takes css selector and its first ancestor

Question 43

How can you remove an element from the DOM?

Answer 43

remove method

Question 44

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

Answer 44

string

Question 45

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

Answer 45

getAttribute