DOM

Question 1

Why do we log things to the console?

Answer 1

so we can check our code for bugs along the way and make sure everything is running without error

Question 2

What is a “model”?

Answer 2

something you want to mirror or follow

Question 3

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

Answer 3

getElementbyId & querySelector

Question 4

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

Answer 4

querySelectorAll

Question 5

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

Answer 5

So you can store the reference or location of the element you’re trying to retrieve into the variable so the browser doesn’t have to keep going back to look for the element

Question 6

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

Answer 6

console.dir

Question 7

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

Answer 7

the HTML document

Question 8

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

Answer 8

javascript objects

Question 9

What is a DOM Tree?

Answer 9

A model of the page when it loads in a browser in the form of a tree.

Question 10

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

Answer 10

the content of the HTML page need to be set first before the dom tree is made

Question 11

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

Answer 11

takes in a css selector and returns the first element that matches

Question 12

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

Answer 12

takes in a css selector and returns a NodeList

Question 13

What is the purpose of events and event handling?

Answer 13

add dynamic content and interactivity. respond to occurrences.

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 is a callback function?

Answer 16

function definition being passed around as a value so it can be invoked later

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

place where the event actually occurred.

Question 19

What is the difference between these two snippets of code?

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

Answer 19

top one is just a callback function that’s being passed around as a value. the second one you’re calling the function right then and there

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

get element from DOM, use className property with assignment operator, and new value

Question 22

What is the textContent property of element objects?

Answer 22

text inside of the element

Question 23

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

Answer 23

get element from DOM and assignment operator with 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

If you wanna do work in JS not very intuitive to go into html and bring it back to do something. Want everything to be in one spot

Question 27

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

Answer 27

no

Question 28

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

Answer 28

appendChild

Question 29

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

Answer 29

attribute and the value of the attribute

Question 30

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

Answer 30

1) querySelector element to be appended to
2) create element
3) append element

Question 31

What is the textContent property of an element object for?

Answer 31

property that holds the text content of the element

Question 32

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

Answer 32

setAttribute, className

Question 33

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

Answer 33

reusability

Question 34

What is the event.target

Answer 34

object that stores the element where the event started

Question 35

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

Answer 35

event bubbling - starts from element where it began and goes up

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

css selector and returns itself or matching ancestor

Question 38

How can you remove an element from the DOM?

Answer 38

remove(). remove() needs to be applied to the specific element you’re trying to 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

put eventlistener on just the parent

Question 40

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

Answer 40

completely hides the element

Question 41

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

Answer 41

selector string 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

every step

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

we’d have to add an event listener to each element

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

you’d need to write a conditional for each view.