Dom manipulation

Question 1

Why do we log things to the console?

Answer 1

To check them

Question 2

What is a “model”?

Answer 2

a version of the page in memory structured to be a DOM tree

Question 3

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

Answer 3

the web page / the tree structure for the web page

Question 4

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

Answer 4

all HTML tags make up the DOM tree as it sees tags as objects / all elements that go into the DOM tree

Question 5

What is a DOM Tree?

Answer 5

it is made up of all the HTML tags / how the DOM structures the model of the web page / kinda like an organization chart CEO at top and alot of workers at the bottom

Question 6

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

Answer 6

querySelector / 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

so it doesn’t have to be searched for every time you want to use it.

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

so all the HTML loads before it

Question 11

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

Answer 11

takes a string or css selector / returns the first matching element

Question 12

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

Answer 12

takes a string or css selector / returns all the matching elements as a NodeList

Question 13

Why do we log things to the console?

Answer 13

to check them

Question 14

What is the purpose of events and event handling?

Answer 14

so we know what the user is doing and how to handle it

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

Question 17

What is a callback function?

Answer 17

function passed into another function as an argument

Question 18

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

Answer 18

event object

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

check by using console.log / console.dir / or mdn
reference to the object onto which the event was dispatched.
element that is being interacted with

Question 20

What is the difference between these two snippets of code?

element. addEventListener(‘click’, handleClick)
element. addEventListener(‘click’, handleClick())

Answer 20

the bottom code calls the function as soon as it loads instead of by the user or when the event is triggered

Question 21

What is the className property of element objects?

Answer 21

className is the attribute for the element

Question 22

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

Answer 22

with the className property and the assignment operator / without = you would just get a list and can log it

Question 23

What is the textContent property of element objects?

Answer 23

The textContent property allows you to
collect or update just the text that is in the
containing element (and its children).

Question 24

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

Answer 24

by changing the textContent property of an element

Question 25

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

Answer 25

Not always useful or needed

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

maybe a little bit harder as you couldn't visually see how many clicks have been done

Question 27

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

Answer 27

So you can can update them as you go on | / so you dont have to keep calling on the DOM

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 ?

Answer 31

submit

Question 32

What does the event.preventDefault() method do?

Answer 32

prevents the event from being handled with its default behavior

Question 33

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

Answer 33

reloads the page and erases the info in the form

Question 34

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

Answer 34

elements

Question 35

What property of form a 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

that you don't know what is it that isn't working

Question 37

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

Answer 37

you can check as you go along and debug

Question 38

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

Answer 38

No it only creates an element

Question 39

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

Answer 39

append child

Question 40

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

Answer 40

2 params the first is the attribute and the second is the value

Question 41

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

Answer 41

create the element, set attributes if any, add text content and then append it

Question 42

What is the textContent property of an element object for?

Answer 42

to add text to the newly created element

Question 43

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

Answer 43

with setAttribute / classList / className

Question 44

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

Answer 44

to procedurally create multiple elements and add them to a page. to dynamically create elements on a page

Question 45

What is the event.target?

Answer 45

what is being target / element that the user 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 / goes up to see if an eventListener is added to any of the parents

Question 47

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

Answer 47

event.target.tagName

Question 48

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

Answer 48

a selector and returns the closest element with the 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?

Answer 50

adding it to a parent / container

Question 51

What is the event.target?

Answer 51

what is being target / element that the user interacted with

Question 52

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

Answer 52

it doesnt display / doesnt show up

Question 53

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

Answer 53

a selector and returns a boolean value (checks if what your checking matches what your returning)

Question 54

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

Answer 54

element.getAttribute

Question 55

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

Answer 55

at every step so you know if your making a mistake

Question 56

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 56

you would have to add an eventListener to every tab that you have and will add

Question 57

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 57

you would have many more if statements to check for each tab/view and add more if you add more on the page

Question 58

How to you store data in localStorage?

Answer 58

with localStorage.setItem(key,value)

Question 59

How to you retrieve data from localStorage?

Answer 59

with localStorage.getItem(key)

Question 60

What data type can localStorage save in the browser?

Answer 60

JSON strings

Question 61

When does the 'beforeunload' event fire on the window object?

Answer 61

if the user tries to leave the page | The beforeunload event is fired when the window, the document and its resources are about to be unloaded.