DOM

Question 1

Why do we log things to the console?

Answer 1

In order to check and debug our work

Question 2

What is a “model”?

Answer 2

DOM is a representation (a separate entity)

Question 3

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

Answer 3

DOCTYPE Html

Question 4

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

Answer 4

Data type (or type of Data)

Question 5

What is a DOM Tree?

Answer 5

Is a JS object for html element including its elements, attributes, values, children, and its children.

Question 6

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

Answer 6

getElementByID

querySelector

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

Easier to retrieve data, which makes it easy to retrieve

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

Html loads from top to bottom

Needs to parse all the elements before

Question 11

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

Answer 11

Returns only the first of the matching elements (selectors for css)

Question 12

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

Answer 12

Returns all of that matches the called element (selector for css)

Question 13

What is the purpose of events and event handling?

Answer 13

To create a reaction from the user upon action

Question 14

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

Answer 14

Not always necessary

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, which is then invoked inside the outer function to complete some kind of routine or action.
It’s in the event listener

Question 17

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

Answer 17

Is an object with huge amount of properties that just occurred (storing lots of data)

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

Is the point of interaction
Element that dispatches the event

Console.log where the event occurred
If there is a div… and there is a button… the target will be button

Question 19

What is the difference between these two snippets of code?

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

Answer 19

handleClick - is a callback function

element.addEventListener(‘click’, handleClick()):
Functions values get RETURNED
This will be undefined
ex) if it gets checked… and stops
EventListener will never be called by user. It’s called by JS

Question 20

What is the className property of element objects?

Answer 20

It’s the property of the element that sets the value of class attribute 
ex) gettingHot.className
This holds the class name value 
Get a new value or set a new value

Question 21

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

Answer 21

You would assign a new value to the object.className or variable.className
Simply assign new value to it

Question 22

What is the textContent property of element objects?

Answer 22

Get or set
textContent property represents the text content of the node and its descendants
textContent returns every element in the node…
(innerText will not return the text of hidden elements)
Example: Var example = document.getElementById(‘diva’).textContent

Question 23

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

Answer 23

You assign the query the DOM to a variable

And assign new variable.ClassName to a new string

Question 24

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

Answer 24

yes

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

Simpler with variables

Question 26

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

Answer 26

Because you can manipulate the variables to be edited and store functions to use for later
Example is countingClicks.textContent = ‘Clicks: ‘ + storageNumberOfClicks

Question 27

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

Answer 27

No, it is not added yet
The element node is created
This is stored in a variable

Question 28

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

Answer 28

Use the .append() method

Question 29

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

Answer 29

With its name and value

Question 30

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

Answer 30

Step 1: createElement() method
Step 2: createTextNode() method (giving it content)
Step 3: appendChild() method (adding to DOM tree, specifies which element)

Question 31

What is the textContent property of an element object for?

Answer 31

For strings

Question 32

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

Answer 32

className method

setAttribute method

Question 33

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

Answer 33

You can loop through each of the items and manipulate it.

Question 34

What is the event.target?

Answer 34

The target property of the Event interface is a reference to the object onto which the event was dispatched