DOM

Question 1

Why do we log things to the console?

Answer 1

to verify code and get information about code

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

data type

Question 5

What is a DOM Tree?

Answer 5

element + content and configuration

Question 6

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

Answer 6

getElementByID or querySelector

Question 7

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

Answer 7

getElementsByClassName, getElementsByTagName, querySelectorAll

Question 8

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

Answer 8

to reuse in the future (stores location of DOM)

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

load the content of all the elements, documents load from top to bottom

Question 11

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

Answer 11

css selector syntax (string), returns only the first element that matches

Question 12

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

Answer 12

css selector (string), returns NodeList

Question 13

What is the purpose of events and event handling?

Answer 13

when an event “fires” , it can be used to trigger a particular function or code

Question 14

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

Answer 14

no, not all parameters are required

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 is a callback function?

Answer 16

A callback function is a function passed into another function as an argument

passing the definition of the function, not the return

Question 17

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

Answer 17

event object that has data about the event that occured

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

event.target is the target element being used / originated from

console.log(event.target)

MDN

Question 19

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

Answer 19

first code is using the handleClick function while the second code is calling the function

Question 20

What is the className property of element objects?

Answer 20

gets and 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

element.className

Question 22

What is the textContent property of element objects?

Answer 22

contains

Question 23

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

Answer 23

element.textcontent = ‘string’

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?

Question 27

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

Answer 27

focus

Question 28

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

Answer 28

blur

Question 29

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

Answer 29

input

Question 30

What event is fired when a user clicks the “submit” button within a <form>?

Answer 30

submit

Question 31

What does the event.preventDefault() method do?

Answer 31

prevents default action of the event

Question 32

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

Answer 32

browser would reload the page with form’s values in the URL

Question 33

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

Answer 33

.elements

Question 34

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

Answer 34

.value

Question 35

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

Answer 35

could be writing bugs

Question 36

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

Answer 36

when writing code, you can see errors as they happen

Question 37

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

Answer 37

no, created and stored in a variable

Question 38

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

Answer 38

.appendChild

Question 39

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

Answer 39

name, value (attribute name, value)

ex. .setAttribute(‘class’, ‘click-button’)

Question 40

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

Answer 40

create the element and store in a variable, give it content, call querySelector to find element and store in variable, append child and add it to the dom

Question 41

What is the textContent property of an element object for?

Answer 41

to return all the text content including all elements (set or get)

Question 42

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

Answer 42

.className property & .setAttribute() method

Question 43

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

Answer 43

only have to write function once so it can be reusable, and have a name to reuse the function

Question 44

What is the event.target?

Answer 44

where the event started

element u clicked on

Question 45

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

Answer 45

event bubbling

Question 46

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

Answer 46

.tagName

all caps

Question 47

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

Answer 47

string of a valid css selector

return closest ancestor element or itself

Question 48

How can you remove an element from the DOM?

Answer 48

.remove() method

Question 49

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 49

add event listener to an ancestor