DOM

Question 1

Why do we log things to the console?

Answer 1

to check the output and help debug

Question 2

What is a “model”?

Answer 2

representation of something

Question 3

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

Answer 3

HTML document

Question 4

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

Answer 4

the objects that comprise the structure and content of a document on the web

Question 5

What is a DOM Tree?

Answer 5

Every element, attribute, and piece of text in the HTML is represented by its own DOM node, which makes up the DOM tree

Question 6

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

Answer 6

getElementById and querySelector

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

To save the location; saves the browser from having to look for it every time.

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

HTML document needs to loads first so javascript can manipulate DOM

Question 11

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

Answer 11

CSS selector string and returns only the first of the matching elements

Question 12

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

Answer 12

CSS selector string and returns all elements that match

Question 13

What is the purpose of events and event handling?

Answer 13

events inform us of user interaction and event handling instructs how to respond to the event

Question 14

What do [] square brackets mean in function and method syntax documentation?

Answer 14

denotes optional

Question 15

What is a callback function?

Answer 15

a function passed into another function as an argument

Question 16

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

Answer 16

event?

Question 17

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

Answer 17

event object

Question 18

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

Answer 18

target property of event; mdn

Question 19

What is the difference between these two snippets of code?

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

Answer 19

presence of parentheses;
the parentheses are omitted where the function is called because they would indicate that the function should run as the page loads (rather than when the event fires)

Question 20

What is the className property of element objects?

Answer 20

DOM property that sets the value of the class attribute of the specified element

Question 21

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

Answer 21

className property

Question 22

What is the textContent property of element objects?

Answer 22

property that represents the text of the node and its descendants; allows text to be collected/updated

Question 23

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

Answer 23

textContent property

Question 24

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

Answer 24

no, because it is not always needed

Question 25

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

Answer 25

more difficult

Question 26

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

Answer 26

to avoid having to search for the information every time that it is needed

Question 27

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

Answer 27

no, simply creates an element that can be added to the DOM tree

Question 28

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

Answer 28

using appendChild()

Question 29

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

Answer 29

string attribute name and attribute value

Question 30

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

Answer 30

createElement(), pick the spot you want to place it in, appendChild()

Question 31

What is the textContent property of an element object for?

Answer 31

represents the text content of the node and its descendants.

Question 32

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

Answer 32

.className and setAttribute()

Question 33

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

Answer 33

reusable, saves time, and minimizes errors?

Question 34

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

Answer 34

event bubbling from most specific to least specific

Question 35

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

Answer 35

tagName property

Question 36

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

Answer 36

takes a string CSS selector as an argument and returns the closest element (which can be itself)

Question 37

How can you remove an element from the DOM?

Answer 37

.remove()

Question 38

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 38

addEventListener to parent rather than the individual child nodes AKA event delegation

Question 39

What is the event.target?

Answer 39

a reference to the object onto which the event was dispatched

Question 40

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

Answer 40

Turns off the display of an element so that it has no effect on layout

Question 41

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

Answer 41

takes a css string selector as the argument and returns a boolean

Question 42

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

Answer 42

.getAttribute()

Question 43

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

Answer 43

after variable declarations

Question 44

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 44

add individual addEventListeners to each child node

Question 45

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 45

a lot of individual conditionals