DOM

Question 1

Why do we log things to the console?

Answer 1

to know what the code is doing

Question 2

What is a “model”?

Answer 2

representation of something;

DOM tree, stored in the browser’s memory

Question 3

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

Answer 3

the entire page

Question 4

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

Answer 4

data types, collection of data

Question 5

What is a DOM Tree?

Answer 5

all the nodes of the elements

Question 6

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

Answer 6

.getElementByID()

.querySelector()

Question 7

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

Answer 7

.getElementsByClassName()

Question 8

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

Answer 8

so the location of the value is saved and JS doesn’t have to find it again

Question 9

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

Answer 9

.dir()

Question 10

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

Answer 10

HTML needs to load first because JS needs to know what to work with

Question 11

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

Answer 11

takes in a CSS selector,

returns the first match of the selector

Question 12

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

Answer 12

takes in a CSS selector,

returns the all the matches of the selector in a node list

Question 13

What is the purpose of events and event handling?

Answer 13

user interaction

Question 14

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

Answer 14

they’re optional

Question 15

What is a callback function?

Answer 15

a function passed into another function as an argument

Question 16

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

Answer 16

the element that the event handler/listener is applied to

Question 17

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

Answer 17

event name & function ?

Question 18

What is the difference between these two snippets of code?

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

Answer 18

first - event is fired when clicked

second - event is fired at run time

Question 19

What is the difference between these two snippets of code?

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

Answer 19

first - event is fired when clicked

second - event is fired at run time

Question 20

What is the className property of element objects?

Answer 20

list of strings with all the class names of the element
changes the class name of elements

Question 21

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

Answer 21

.className

Question 22

What is the textContent property of element objects?

Answer 22

can change text content in an element

Question 23

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

Answer 23

.textContent

Question 24

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

Answer 24

no

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 complicated

Question 26

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

Answer 26

incase of future uses

Question 27

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

Answer 27

no it just creates one

Question 28

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

Answer 28

element.appendChild(elementYouWantAdded)

Question 29

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

Answer 29

(name, value)

Question 30

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

Answer 30

1. Create element node
2. Create text node
3. Add text node to element node
   or
4. Add textContent to node
5. Add element to dom tree

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

1. .className

2. .setAttribute(class, value)

Question 33

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

Answer 33

1. It can create the tree with a lot of elements in one go instead of manually inputting
2. reduces human error like spelling mistakes

Question 34

What is the event.target?

Answer 34

whatever part of the document I am clicking on

Question 35

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

Answer 35

bubbling

Question 36

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

Answer 36

.tagName

Question 37

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

Answer 37

argument - selectors

returns closest ancestor element

Question 38

How can you remove an element from the DOM?

Answer 38

elementName.remove()

Question 39

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 39

apply event listener to the parent element