W4. Asynch & State - Cookies and local storage

Question 1

What are cookies used for?

Answer 1

• cookies provide a small amount of client-side storage
• keep preferences
• config info
• returning visitors
• info to re-use later in application
  (Cookies and local storage add state)

Question 2

What does cookie storage look like?

Answer 2

Cookie strings have key-value pairs

name1=value1;name2=value2;name3=value3

Question 3

Give some examples of pre-defined cookie fields

Answer 3

• path
• domain
• max-age
• expires
• secure

Question 4

What is LocalStorage for HTML5?

Answer 4

Alternative API for HTML5 for managing cookies, adds better support for local state
SessionStorage - managing a connected session, rather than a specific domain
Cleaner API for manipulating key-value pairs

Question 5

Give examples of some methods in the LocalStorage API

Answer 5

• clear() cookie for that page
• getItem(key) key for which a value has been set
• setItem(key, value) set key, value pair
• removeItem(key) remove key, value pair for key

Question 6

What is a session?

Answer 6

• single use of a page
• application level session extending beyond lifetime of a single transport level connection
• long-lived application level interaction for a user

Question 7

What possible privacy considerations are there when using Cookies and LocalStorage?

Answer 7

• both are used to track users: info between sites, sites visited, info input from session
• cookies are all plain text
• any server can set a cookie in an HTTP response (pages with 3rd party content)
• GDPR: opt-in policy for use of tracking cookies