DOM

Question 1

Why do we log things to the console?

Answer 1

To be aware of what our code Is doing and to make sure it has the outcome we want

Question 2

What is a “model”?

Answer 2

A replication of a dom tree that is stored in the browser’s terminal

Question 3

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

Answer 3

the HTML document we are working on

Question 4

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

Answer 4

Each object refers to a different part of the page in the browser

Question 5

What is a DOM Tree?

Answer 5

Collection of all the objects that make up the document

Question 6

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

Answer 6

Document.getElementById() & document.querySelector()

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

If you know that you need to call on that query multiple times

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 it can run the entire body to map out a tree before running our script

Question 11

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

Answer 11

Takes our class or id as an argument and returns the first instance of it

Question 12

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

Answer 12

Takes all the elements or class we are looking for and returns a nodes list

Question 13

What are some differences of Nodes list and HTML collection?

Answer 13

o Html collection will live update as you add things
o Nodes list is static and would not update

Question 14

What is the purpose of events and event handling?

Answer 14

Events will trigger code. Event handling is to run blocks of code based on what happens on our webpage

Question 15

What method of element objects let 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 function passed into another function as an argument which is then invoked inside the outer function to complete some kind of action

Question 17

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

Answer 17

The event object. It gives us information about the event that actually occurs

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

The specific html element that was interacted with and that caused it to occur

Question 19

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

Answer 19

a function without the parenthesis is a reference to the function. With parenthesis you are actually calling it.

Question 20

What is the className property of element objects?

Answer 20

the current classes on the object and allows us to dynamically update it

Question 21

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

Answer 21

By using .className = and then the name you want to change it to

Question 22

What is the textContent property of element objects?

Answer 22

It represents the text content of the node and its descendants

Question 23

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

Answer 23

Calling that element.textContent = the new value you want to assign to that element

Question 24

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

Answer 24

It is useful but sometimes you do not need it, sometimes it is useful to know what the function is expecting in its parameter though

Question 24

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

Answer 24

It is useful but sometimes you do not need it, sometimes it is useful to know what the function is expecting in its parameter though

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 because we would have to query the dom everytime we needed to use an element. Instead we can just store the results so it does not have to query again

Question 26

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

Answer 26

Because the variable will always be able to find where that information is without having to go through the whole html file first
The dom will be dynamic and constantly be changing things

Question 27

What happens if you do not give .className a value?

Answer 27

it will just tell you what the class is doing

Question 28

Why is innerHTML bad?

Answer 28

Puts exposure to hacking

Question 29

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

Answer 29

No

Question 30

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

Answer 30

appendChild() method

Question 31

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

Answer 31

Name, value

Question 32

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

Answer 32

Create it and then append it to something

Question 33

What is the textContent property of an element object for?

Answer 33

You can get textContent and use it to set textContent

Question 34

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

Answer 34

setAttribute & className

Question 35

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

Answer 35

Main advantage is that it is reusable

Question 36

What is the event.target?

Answer 36

o it is a reference to the object which the event is occuring to
o whatever element that was actually interacted with

Question 37

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

Answer 37

Happens on the child and bubbles upward

Question 38

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

Answer 38

o .tagName
o It will tell you which element you are actually interacting with if you use a ‘click’ event

Question 39

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

Answer 39

o This method will go from the current element to whichever id, class, or element you put in as an argument
o Css selector and will return the first one that matches it

Question 40

How can you remove an element from the DOM?

Answer 40

Item you want to remove .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

Add the event listener to the parent so that you will capture everything that happens to its children