DOM

Question 1

Why do we log things to the console?

Answer 1

to keep a record of the output (self-check)

Question 2

What is a “model”?

Answer 2

a representation of the the actual thing, recreation of something

Question 3

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

Answer 3

it would be the HTML document

Question 4

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

Answer 4

the data type (elements) from the HTML

Question 5

What is a DOM Tree?

Answer 5

it is a layout like a family tree that consists of HTML elements and how they connect to each other. Body element with all of its child elements and the content it holds.

Question 6

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

Answer 6

getElementById, querySelector(‘CSS selector’)

Question 7

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

Answer 7

getElementByClassName(‘class’),

Question 8

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

Answer 8

in the future for reference, it is much easier and efficient to assign it to a variable for faster access.

Question 9

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

Answer 9

console.dir; the directory method of the console object.

Question 10

Why would a tag need to be placed at the bottom of the HTML content instead of at the top?

Answer 10

the browser reads the code from top to bottom. In the JS when referring to elements (objects) there is nothing to refer to.

Question 11

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

Answer 11

it takes a string which is a CSS selector as arguments and returns the first element that matches the selector

Question 12

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

Answer 12

it takes a selector as an argument and returns a list of properties of that object which is called a node list.

Question 13

Why do we log things to the console?

Answer 13

to keep track of our output and see if our code at each code

Question 14

What is the purpose of events and event handling?

Answer 14

it is for a function or action to be performed when and after a user interacts with the page itself.

Question 15

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

Answer 15

No, not all the parameters are needed (boolean).

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 a callback function?

Answer 17

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.

Question 18

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

Answer 18

it is the object created by the JS engine and relays all the information about the object

Question 19

What is the event.target? If you weren’t sure, how would you check? Where could you get more information about it?

Answer 19

it is the read-on property target of the object event. You could check the console. Go onto MDN. Where the event occurred (started).

Question 20

What is the difference between these two snippets of code?

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

Answer 20

First, the second argument is a callback function. Second, the second argument is the return of the function is being called, which makes the function work. We cannot pass the work as an argument.

Question 21

What is the className property of element objects?

Answer 21

The className property of the Element interface gets and sets the value of the class attribute of the specified element. Format is a string and the this needs to be the full string.

Question 22

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

Answer 22

using the property.className = “and new value of that property.

Question 23

What is the textContent property of element objects?

Answer 23

it represents the text content of the node and its descendants.

Question 24

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

Answer 24

by using the text.Content property

Question 25

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

Answer 25

not always useful

Question 26

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

Answer 26

more complicated because wouldnt be able to keep track of the # of clicks, and would have to go back into the DOM to retrieve that element

Question 27

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

Answer 27

You are able to access it in the future. easy to update and visible.

Question 28

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

Answer 28

focus

Question 29

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

Answer 29

blur

Question 30

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

Answer 30

input

Question 31

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

Answer 31

submit

Question 32

What does the event.preventDefault() method do?

Answer 32

stops the page from refreshing…The preventDefault() method of the Event interface tells the user agent that if the event does not get explicitly handled, its default action should not be taken as it normally would be.
checkbox example on MDN

Question 33

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

Answer 33

does not refresh the page.

Question 34

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

Answer 34

elements property which are input, button, textarea….

Question 35

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

Answer 35

.value

Question 36

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

Answer 36

ultimately there is a chance it wont work, so checking it helps you know what exactly does not work. try to use console.log!

Question 37

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

Answer 37

Being able to see if anything goes wrong with the code. being able to see if an error is about to happen when saving.

Question 38

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

Answer 38

no, it needs to be appended to the parent element first or the DOM tree

Question 39

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

Answer 39

.appendChild() to the parent element

Question 40

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

Answer 40

the keyword of the attribute and the value in strings

Question 41

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

Answer 41

document.createElement(‘element’) assigned to a new variable, then if need be a text create a new variable with the value being .createTextNode(), and then append that textNode to the element and then append that element to a parent element

Question 42

What is the textContent property of an element object for?

Answer 42

to add text to an element

Question 43

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

Answer 43

setAttribute() and the className

Question 44

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

Answer 44

you are able to adjust the format of the app, and we can reuse that function over and over again
and you can you that DOM tree in multiple applications