DOMS

Question 1

Why do we log things to the console?

Answer 1

To debug and verify

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

It refers to the fact that each node is an object.

Node (for our purposes most likely refers to an HTML element)

Question 4

What is a DOM Tree?

Answer 4

An element and all of its content

Question 5

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

Answer 5

querySelector

getElementById

Question 6

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

Answer 6

querySelectorAll

Question 7

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

Answer 7

You might need to work with an element multiple times, so the computer doesn’t have to constantly look for that reference to the variable.

Question 8

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

Answer 8

dir

Question 9

why would a script tag need to be placed at the bottom of the HTML content instead of the top?

Answer 9

Because if you put it on the top, the html code isn’t loaded yet, and you can’t access the elements.

Question 10

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

Answer 10

CSS selector

returns the JS object

Question 11

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

Answer 11

CSS selector

returns a node list

Question 12

Why do we log things to the console?

Answer 12

Debugging and verification

Question 13

What is the purpose of events and event handling?

Answer 13

When you want to do something when something else occurs.

Question 14

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

Answer 14

addEventListener()

Question 15

What is a callback function?

Answer 15

It is a function used as an argument in another function.

Question 16

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

Answer 16

It is the object of the event that was used
e.g. function handleDoubleClick(event) {}
You don’t define the event parameter yourself
- JavaScript prepacks it with all the information about the type of event handleDoubleClick is used with addEventListener

Question 17

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

Answer 17

The event target is a reference to the object that caused the event to happen.

use the console and look at MDN

The target is where the event directly occurred from.

Question 18

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

Answer 18

o element.addEventListener(‘click’, handleClick)
- runs when the event happens
o element.addEventListener(‘click’, handleClick())
- runs when the page loads

Question 19

What is the className property of element objects?

Answer 19

It is the value of the class attribute.

Question 20

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

Answer 20

variableName.className = “new class”

variableName.classList.add(‘newClass’)

variableName.classList.remove(‘removeThisClass’)

Question 21

What is the textContent property of element objects?

Answer 21

It gives you access to the text content within an element.

Question 22

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

Answer 22

variableName.textContent = new value

Question 23

Is the event parameter of an event listener always useful?

Answer 23

no

Question 24

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

Answer 24

More complicated

Question 25

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

Answer 25

It lets you quickly access it whenever you need it.

Question 26

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

Answer 26

focus

Question 27

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

Answer 27

input

Question 28

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

Answer 28

submit

Question 29

what does the event.preventDefault() method do?

Answer 29

It stops the event from doing what it normally does?

Question 30

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

Answer 30

The data will be sent somewhere and the page will reload

Question 31

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

Answer 31

Elements

Question 32

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

Answer 32

.value

Question 33

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

Answer 33

no

Question 34

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

Answer 34

Append child

Question 35

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

Answer 35

attribute name and value

Question 36

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

Answer 36

Create element node
Retrieve the element you want to append to the node
Append the element to the node
Add node to DOM tree

Question 37

What is the textContent property of an element object for?

Answer 37

Retrieve or change text content in a node

Question 38

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

Answer 38

setAttribute()

className

Question 39

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

Answer 39

You can reuse the function.

It makes code more readable.

Question 40

What is the event.target

Answer 40

It is where the event occurred from

Question 41

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

Answer 41

event bubbling

Question 42

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

Answer 42

tagName

Question 43

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

Answer 43

Selector

returns the closest node that matches the given selector up the ancestor

Question 44

How can you remove an element from the DOM?

Answer 44

.remove()

Question 45

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?

Answer 45

You put the event on the least specific node (probably the container)

Question 46

What is the event.target?

Answer 46

It is the element where the event occurred from

Question 47

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

Answer 47

It makes the element act as if it doesn’t exist

Question 48

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

Answer 48

selector

boolean

Question 49

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

Answer 49

getAttribute()

Question 50

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

Answer 50

When you need to see if something is working the way you intend it to