json

Question 1

What is JSON?

Answer 1

data interchange format used to send and store information in computer systems; text-based data format; exists as a string and needs to be converted to a native js object when you want to access the data

Question 2

What are serialization and deserialization?

Answer 2

serialization: converting a native object to a string so it can be transmitted across the network
deserialization: converting a string to a native object

Question 3

Why are serialization and deserialization useful?

Answer 3

transmit data across a network

Question 4

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

Answer 4

JSON.stringify: converts a JavaScript object or value to a JSON string

Question 5

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

Answer 5

JSON.parse: parses a JSON string, constructing the JavaScript value or object described by the string

Question 6

json and strings

Answer 6

JSON requires double quotes to be used around strings and property names. Single quotes are not valid other than surrounding the entire JSON string

Question 7

simplest json

Answer 7

a single string or number would be valid JSON; can actually take the form of any data type that is valid for inclusion

Question 8

How to you store data in localStorage?

Answer 8

first, use the stringify method of the json object to turn the data (the argument of the method) to a string

then use the

set item method of the local storage object with two arguments, key name and key value

Question 9

How to you retrieve data from localStorage?

Answer 9

get item method of the local storage object with the kay name as the argument

Question 10

What data type can localStorage save in the browser?

Answer 10

strings; not objects nor arrays

Question 11

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

Answer 11

when the window, the document and its resources are about to be unloaded; a confirmation dialog asking the user if they really want to leave the page; to show the confirmation dialog an event handler should call preventDefault() on the event

Question 12

setItem

Answer 12

arg:
- keyname: A DOMString containing the name of the key you want to create/update.
- key value: A DOMString containing the value you want to give the key you are creating/updating.
return: undefined

Question 13

getItem

Answer 13

arg: A DOMString containing the name of the key you want to retrieve the value of
return: A DOMString containing the value of the key. If the key does not exist, null is returned

use a if statement after get

Question 14

Window.localStorage

Answer 14

The localStorage read-only property of the window interface allows you to access a Storage object for the Document’s origin; the stored data is saved across browser sessions; value: a Storage object which can be used to access the current origin’s local storage space

Question 15

how to clear local storage?

Answer 15

use the delete method, i.e., localStorage.clear();

set the data to empty set