JS

Question 1

How to you store data in localStorage?

Answer 1

localStorage.setItem(‘myCat’, ‘Tom’);

Question 2

How to you retrieve data from localStorage?

Answer 2

localStorage.getItem(‘myCat’);

Question 3

What data type can localStorage save in the browser?

Answer 3

only strings

Question 4

When does the ‘beforeunload’ event fire on the window object?

Answer 4

when the document and it’s resources are about to be unloaded, or closing the browser

Question 5

What is JSON?

Answer 5

text-based data format following JavaScript object syntax

Question 6

What are serialization and deserialization?

Answer 6

Serialization is the process of turning an object in memory into a stream of bytes so you can do stuff like store it on disk or send it over the network. Deserialization is the reverse process: turning a stream of bytes into an object in memory.

Question 7

How do you serialize a data structure into a JSON string using JavaScript?

Answer 7

JSON.Strignify

Question 8

How do you deserialize a JSON string into a data structure using JavaScript?

Answer 8

JSON.Parse

Question 9

What is the event.target?

Answer 9

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

Question 10

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

Answer 10

it makes it invisible and takes it out of document

Question 11

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

Answer 11

it takes an argument of css selector, returns a boolean, weather css selector matches the element

Question 12

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

Answer 12

get attribute method

Question 13

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

Answer 13

every step

Question 14

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 14

you would have to list every tab element with multiple listeners

Question 15

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 15

you need a list of explicit conditionals,

Question 16

What is the event.target?

Answer 16

target property of the event interface, reference to the object which event was dispatched

Question 17

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

Answer 17

because of the default document flow, which is set to event bulling, so starts at the most specific elements, then less specific

Question 18

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

Answer 18

event.target

Question 19

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

Answer 19

the argument is a selector and it returns it’s self or nearest ancestor element

Question 20

How can you remove an element from the DOM?

Answer 20

use .remove method

Question 21

f 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 21

you would add an event listener to the parent, using event delegation

Question 22

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

Answer 22

no, it just simply create the element,that’s going to be added to the dom

Question 23

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

Answer 23

append child method

Question 24

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

Answer 24

attribute name and the value

Question 25

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

Answer 25

create element, grab the spot you want to append it to, append it

Question 26

What is the textContent property of an element object for?

Answer 26

assigning text content to the new element, and also for knowing the text content in the text element

Question 27

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

Answer 27

assigning a new name to the class property and the other way is set attribute

Question 28

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

Answer 28

repetition and make it dynamic

Question 29

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

Answer 29

focus

Question 30

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

Answer 30

blur

Question 31

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

Answer 31

input

Question 32

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

Answer 32

submit

Question 33

What does the event.preventDefault() method do?

Answer 33

if the event is not explicitly handled, its default action should be taken

Question 34

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

Answer 34

refreshes the page and adds the data on the url

Question 35

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

Answer 35

elements property

Question 36

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

Answer 36

value property