DOM

Question 1

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

Answer 1

takes a css selector and returns a node list

Question 2

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

Answer 2

takes a css selector and returns a single node

Question 3

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

Answer 3

so that everything else could load first

Question 4

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

Answer 4

console.dir()

Question 5

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

Answer 5

you use it frequently

Question 6

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

Answer 6

objects are what comprise the web page

Question 7

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

Answer 7

document node

Question 8

What is a DOM Tree?

Answer 8

dom element with its components it consists of four nodes: document node, element nodes, attribute nodes, and text nodes

Question 9

Why do we log things to the console?

Answer 9

we log things to the console to know what we are doing and to check that our work is valid

Question 10

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

Answer 10

html

Question 11

What is a “model”?

Answer 11

representation of something

Question 12

Why do we log things to the console?

Answer 12

we log things to the console to know what we are doing and to check that our work is valid

Question 13

What is the purpose of events and event handling?

Answer 13

user interactivity

Question 14

Are all possible parameters required to use a JavaScript method or function?

Answer 14

no

Question 15

What method of element objects lets you set up a function to be called when a specific type of event occurs?

Answer 15

.addEventListener()

Question 16

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

Answer 16

event object; all of the data that a browser feels is pertinent to that event

Question 17

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

Answer 17

the target property of the event interface is a reference to the object onto which the event was dispatched

check on mdn

basically, which object was the event acted upon?

Question 18

What is the difference between these two snippets of code?

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

Answer 18

the first is using a callback function while the second is immediately calling the function

Question 19

What is the className property of element objects?

Answer 19

the className property gets and sets the value of the class attribute of the specified element

Question 20

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

Answer 20

use the className property

Question 21

What is the textContent property of element objects?

Answer 21

it is whatever text is written for the object

Question 22

What is the textContent property of element objects?

Answer 22

text inside of the element

Question 23

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

Answer 23

it is not always useful

Question 24

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

Answer 24

it would be more complicated because we would have to

Question 25

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

Answer 25

you don't have to keep searching for the information in the dom

Question 26

What event is fired when a user places their cursor in a form control?

Answer 26

focus

Question 27

What event is fired when a user's cursor leaves a form control?

Answer 27

blur

Question 28

What event is fired as a user changes the value of a form control?

Answer 28

input

Question 29

What event is fired when a user clicks the "submit" button within a ?

Answer 29

submit

Question 30

What does the event.preventDefault() method do?

Answer 30

if the event does not get explicitly handled, its default action should not be taken as it normally would be

Question 31

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

Answer 31

it refreshes the page immediately

Question 32

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

Answer 32

element

Question 33

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

Answer 33

value

Question 34

What is one risk of writing a lot of code without checking to see if it works so far?

Answer 34

one part of the code may be broken and it would be a hassle to track through all the code to find what is broken

Question 35

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

Answer 35

you can immediately detect when there is an error message

Question 36

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

Answer 36

no

Question 37

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

Answer 37

appendChild()

Question 38

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

Answer 38

name, value

Question 39

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

Answer 39

query document, create element, append element

Question 40

What is the textContent property of an element object for?

Answer 40

see the text content

Question 41

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

Answer 41

className and setAttribute

Question 42

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

Answer 42

reusability, no need to create another function in a different area so more control

Question 43

Give two examples of media features that you can query in an @media rule

Answer 43

placeholder

Question 44

Which HTML meta tag is used in mobile-responsive web pages?

Answer 44

placeholder

Question 45

What is the event.target?

Answer 45

this is the element to which the event happened to

Question 46

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

Answer 46

bubbling

Question 47

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

Answer 47

element.target.nodeName | tagName

Question 48

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

Answer 48

this traverses the element and its parent until it finds a node that matches the provided selector string and it will return itself or the matching ancestor; if no such element exists, it returns null

Question 49

How can you remove an element from the DOM?

Answer 49

use .remove() method

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

parent element