DOM

Question 1

Why do we log things to the console?

Answer 1

For debugging and/or making sure things work

Question 2

What is a “model”?

Answer 2

Layout of the html document as a tree of objects

Question 3

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

Answer 3

HTML

Question 4

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

Answer 4

HTML elements as objects

Question 5

What is a DOM Tree?

Answer 5

The HTML document in the form of a model of objects that looks like a tree

Question 6

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

Answer 6

document.queryselector()
document.getElementById()

Question 7

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

Answer 7

document.querySelectorAll()

Question 8

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

Answer 8

So you can access it later

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

If it was at the top, the website would stop loading until all of the javascript was downloaded

Question 11

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

Answer 11

CSS selector as argument
Returns an element object representing the first element in the document that matches the selector

Question 12

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

Answer 12

CSS selector as argument
Returns a NodeList containing one element object for each element that matches the selector

Question 13

What is the purpose of events and event handling?

Answer 13

Handler is called by listener (I write handler)

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

Event listener

Question 16

What is a callback function?

Question 17

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

Answer 17

event

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

Returns the element that triggered the event

Question 19

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

Answer 19

focus

Question 20

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

Answer 20

blur

Question 21

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

Answer 21

input

Question 22

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

Answer 22

submit

Question 23

What does the event.preventDefault() method do?

Answer 23

Prevents default behavior of the event

Question 24

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

Answer 24

refreshes the page

Question 25

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

Answer 25

form.elements

Question 26

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

Answer 26

value property

Question 27

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

Answer 27

Bugs/errors

Question 28

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

Answer 28

To check for bugs/errors

Question 29

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

Answer 29

It doesn’t until it is appended

Question 30

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

Answer 30

document.appendChild()

Question 31

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

Answer 31

Name of the attribute, value

Question 32

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

Answer 32

createElement -> append

Question 33

What is the textContent property of an element object for?

Answer 33

The text for the element

Question 34

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

Answer 34

classname or setAttribute or classList

Question 35

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

Answer 35

You can create it for multiple items at once, and since it’s a function it will be there for later use?

Question 36

What is the event.target?

Answer 36

It’s what element the user interacted with

Question 37

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

Answer 37

Bubbling

Question 38

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

Answer 38

event.target.tagName

Question 39

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

Answer 39

Css selector and returns the closest upward element or parent selected

Question 40

How can you remove an element from the DOM?

Answer 40

remove()

Question 41

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 41

Adding an event listener to the parent element

Question 42

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

Answer 42

Removed from page

Question 43

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

Answer 43

make sure an element has a css selector

Question 44

How can you retrieve the value of an element’s attribute?

Answer 44

.getAttribute()

Question 45

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 45

Separate event handlers for each event listener

Question 46

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 46

Individual conditionals