DOM

Question 1

Why do we log things to the console?

Answer 1

to debug things and figure it all out

Question 2

What is a “model”?

Answer 2

something recreating or ‘modeling’ something else
a tree of the stuff in the html

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

refers to the data type object in js

Question 5

What is a DOM Tree?

Answer 5

a model of a webpage
-an element + all its configuration + all its contents, represented as an object in the dom

Question 6

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

Answer 6

getelementbyid, queryselector
-the only method you ever need to use to retrieve 1 thing from dom is 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

store it incase you need to use it more. Otherwise, you’ll have to query something 100x
storing as variables > queryselectoring x 100, because queryselectoring searches the whole page a lot

Question 9

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

Answer 9

document.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

because you need to scan through the whole page to find stuff
your js would load before your html that it references

if you queryselector something that doesn’t exist, u get null
script at bottom is important

Question 11

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

Answer 11

it takes a css selector, it returns the element and its stuff

Question 12

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

Answer 12

takes a css selector, returns a nodelist containing all the elements

Question 13

Nodes? Nodelists?

Answer 13

nodelists -> a collection of nodes. Not arrays, just a collection

Nodes -> The DOM Node interface is an abstract base class upon which many other DOM API objects are based, thus letting those object types to be used similarly and often interchangeably. As an abstract class, there is no such thing as a plain Node object. All objects that implement Node functionality are based on one of its subclasses. Most notable are Document, Element, and DocumentFragment.

Question 14

What is the purpose of events and event handling?

Answer 14

it makes the page intractable

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(‘eventtypehere’, function)

Question 17

What is a callback function?

Answer 17

when you pass a function as an argument to another function

yo dawg i heard u like functions

Question 18

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

Answer 18

an object with a bunch of data to describe the event that occured… the “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

its the element where the event originated from.

Question 20

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

Answer 20

2nd one calls it right that second and will run it before the click ever happens and it never ends up being an event handler

1st one callbacks a function

Question 21

What is the className property of element objects?

Answer 21

it gets and sets the current classes applied to the element

literally the value of the class attribute

it’s NOT a css selector

Question 22

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

Answer 22

element.classname = ‘agjkafkg’

Question 23

What is the textContent property of element objects?

Answer 23

allows you to get or set the text of the element

Question 24

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

Answer 24

element.textcontent = “jakldjfklasdjflk”

Question 25

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

Answer 25

no, but MOST of the time it will

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

complicated

Question 27

Why is storing information about a program in variables better than only storing it in 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 <form>?

Answer 31

submit

dont put submit event handler on submit button… needs to be on the form itself

NEVER EVER have a click event listener on submit button

Question 32

What does the event.preventDefault() method do?

Answer 32

prevents default behavior of the event

need it for forms because of the way forms were originally programmed. Things have changed

Question 33

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

Answer 33

it prevents the page from automatically reloading with the form’s values in the URL

ALWAYS CALL THIS SHIT

Question 34

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

Answer 34

form.elements,

Question 35

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

Answer 35

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

if it doesn’t work from like line 2 and you’re on 50 lines, you won’t know what works and what doesnt

Question 37

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

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

parent.appendchild(child)

Question 40

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

Answer 40

setAttribute(‘nameofvalueyouwannachange’, ‘whatyouwannachangeitto’)

Question 41

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

Answer 41

query where you wanna put it first…. unless you already did that

create the element, give it content(textnode), appendchild

Question 42

What is the textContent property of an element object for?

Answer 42

add text OR see text of a current element

Question 43

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

Answer 43

className, or setAttribute

also, classList, which has a set of methods for stuff

classname classlist setattribute are basically personal choice.
changing 1 class value? classlist probably good
changing the whole class thingy? setattribute prob good

Question 44

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

Question 45

what is the affect of display.none?

Answer 45

it makes it disappear

Question 46

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

Answer 46

takes css selector, returns boolean (for whether or not the selector matches)

Question 47

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

Answer 47

getattributes() - use the name of the attribute u want

Question 48

if you were to add another tab and view to your html, but didnt use event delegation, how would your js code be written instead

Answer 48

need conditionals for each possible view

Question 49

if you didnt use a loop to conditionally show or hide the views in the page, how would your js code be written instead