DOM

Question 1

Why do we log things to the console?

Answer 1

verify values to help debug

Question 2

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

Answer 2

the entire page (html)

Question 3

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

Answer 3

the entire page (html document)

Question 4

What is a DOM Tree?

Answer 4

a model of the web page (html doc) as a javascript object

Question 5

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

Answer 5

querySelectorAll()

Question 6

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

Answer 6

in case you need to work with the element more han once

Question 7

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

Answer 7

console.dir()

Question 8

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

Answer 8

the rest of the page must be loaded to create an accurate DOM tree

Question 9

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

Answer 9

the rest of the page must be loaded/created to create an accurate DOM tree

Question 10

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

Answer 10

CSS selector; returns all matching element

Question 11

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

Answer 11

CSS selector; returns all matching element in the form of a node list

Question 12

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

Answer 12

a data type in javascript which can hold multiple items

Question 13

Why do we log things to the console?

Answer 13

check things

Question 14

What is the purpose of events and event handling?

Answer 14

respond to occurrences

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 definition being passed around as a value to be invoked later

Question 18

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

Answer 18

all possible data the browser feels would be pertinent to the event

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

specifies where the event occurs

Question 20

What is the difference between these two snippets of code?

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

Answer 20

second snippet would result in an error as no arguments would have been passed in

Question 21

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

Answer 21

using the .className method

Question 22

What is the textContent property of element objects?

Answer 22

represents text content of the node

Question 23

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

Answer 23

get element from dom, then use textContent property to change

Question 24

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

Answer 24

no, event doesn’t always need to be used

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

significantly more complicated

Question 26

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

Answer 26

more readily available in a variable

also easier than searching through the entire DOM