DOM

Question 1

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

Answer 1

querySelector() and getElementById()

Question 2

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

Answer 2

QuerySelectorAll()

Question 3

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

Answer 3

Its easier to find if the browser needs to use the same elements more than once.

Question 4

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

Answer 4

Console.dir()

Question 5

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

Answer 5

So it can create a model after the document.

Question 6

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

Answer 6

Selectors, and it returns an HTML element object representing the first element in the document that matches the specified set of CSS selectors, or null is returned if it doesn’t find a match.

Question 7

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

Answer 7

Selectors and it returns a nodelist or an empty nodelist if it doesn’t find any matches.

Question 8

What method of element objects lets u set up a function to be called when a specific type of event occurs?

Answer 8

the eventTarget.addeventListener();

Question 9

What is a callback function

Answer 9

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 10

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

Answer 10

The event object.

Question 11

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

Answer 11

The target property of the event interface which references the object onto which the event was dispatched. Console.log(), MDN?

Question 12

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

Answer 12

the first waits for the event to happen then fires the function and the second one fires the event when the page gets loaded.

Question 13

what do [ ] square brackets mean in function and method syntax documentation?

Answer 13

optional parameters

Question 14

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

Answer 14

No it just creates an element

Question 15

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

Answer 15

appendChild() method

Question 16

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

Answer 16

name and value

Question 17

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

Answer 17

Create the element create elements nested into the outer element and append them to said element.

Question 18

What is the text content property of an element object for?

Answer 18

To retrieve or replace the text content in the dom element

Question 19

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

Answer 19

setAttribute(); and .className

Question 20

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

Answer 20

you dont have to go into the HTML document to create it and everything is all in one spot?

it lets you use it where ever you want and you can reuse it.

Question 21

what is the event.target?

Answer 21

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

Question 22

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

Answer 22

because of event bubbling.

Question 23

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

Answer 23

element.tagName

Question 24

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

Answer 24

the closest method returns the first encounter ancestor element that matches the selector provided

Question 25

How can you remove an element from the DOM?

Answer 25

the remove() method

Question 26

If you want 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 26

By just targeting the parent element and putting it on the element that holds the element.

Question 27

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

Answer 27

it disappears

Question 28

what does the element.match() method take as an argument and what does it return

Answer 28

Selector string as an argument

Question 29

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

Answer 29

every step of the way

Question 30

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 30

we’d have to add an event listener to each element.

Question 31

if you didn’t use a loop to continually show or hide the views in the page, how would your javascript code be written instead?

Answer 31

you’d need a conditional for each view.

Question 32

How can you retrieve the value of an elements attribute?

Answer 32

getAttribute()