DOM

Question 1

Why do we log things to the console?

Answer 1

to check the result of element

Question 2

What is a “model”?

Answer 2

representation of an actual thing

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

JavaScript

Question 5

What is a DOM Tree?

Answer 5

tree data structure of HTML page

Question 6

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

Answer 6

queryselector & getElementById

Question 7

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

Answer 7

querySelectorAll

Question 8

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

Answer 8

to reuse the result again

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

so that dom element gets loaded before javascript try to get elements

Question 11

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

Answer 11

selector element and result first match

Question 12

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

Answer 12

selector element and result is all-match

Question 13

Why do we log things to the console?

Answer 13

to debugging

Question 14

What is the purpose of events and event handling?

Answer 14

to perform some action base on user action

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 the className property of element objects?

Answer 17

its use to get and update class name of element

Question 18

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

Answer 18

get element using className

Question 19

What is the textContent property of element objects?

Answer 19

It can get or update the element text content

Question 20

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

Answer 20

using element.textContetent = value

Question 21

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

Answer 21

No

Question 22

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

Answer 22

more complicated

Question 23

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

Answer 23

to get specific element property multiple time and going through dom each time is not effective its better to store it to the variable

Question 24

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

Answer 24

no it does not

Question 25

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

Answer 25

parentName.appenchild(childName)

Question 26

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

Answer 26

name of the attribute

Question 27

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

Answer 27

createElement() put it into variable createTextNode() to create text appendChild where to put the element

Question 28

What is the textContent property of an element object for?

Answer 28

to get or add text content to the element

Question 29

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

Answer 29

set attribute and class name

Question 30

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

Answer 30

reuse the code

Question 31

What is the event.target?

Answer 31

its return where the event occure

Question 32

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

Answer 32

bcas it carried forward to its ancestors

Question 33

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

Answer 33

tagName property

Question 34

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

Answer 34

it take css selector and return the closest one

Question 35

How can you remove an element from the DOM?

Answer 35

remove() method on DOM element

Question 36

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 36

add it to one layer above and listen to that event

Question 37

What is the event.target?

Answer 37

shows where event was trigger

Question 38

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

Answer 38

remove from document flow

Question 39

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

Answer 39

boolean value

Question 40

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

Answer 40

getAttribute() method

Question 41

At what steps of the solution would it be helpful to log things to the console?

Answer 41

every step

Question 42

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 42

then need to write event for each element

Question 43

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 43

we have to write if condition for each node