W2. Computation

Question 1

Describe the OG web model

Answer 1

• client sends request
• server returns page
• web pages stored in files on server
  Everything is static!

Question 2

Describe the modern web model

Answer 2

• dynamic content/input
• personalised data on pages
• can upload info from client to server (info in both directions)
• client-side state (asynch & caching)
• validation on client & server sides
• fetch new info dynamically

Question 3

List technologies needed to create dynamic web pages

Answer 3

• Event handlers in HTML
• Handlers calling client-side JS
• JS manipulates the DOM
• Some language server-side (JS for code re-usability)

Question 4

In JS, what does dynamic typing mean?

Answer 4

Type of a variable is assigned when the value is assigned
- type may also be changed if value is re-assigned
(but typing is strong)

Question 5

In JS, what are the primitive types?

Answer 5

• numbers
• strings
• booleans

Question 6

In JS, what are the trivial types?

Answer 6

• null

- undefined

Question 7

In JS, what are the composite types?

Answer 7

• objects

- arrays

Question 8

In JS, what properties do functions have as types?

Answer 8

• functions are first-class values

- there are multiple ways of defining functions

Question 9

What is the difference between using == and === in JS?

Answer 9

== checks if two values are the same regardless of type (coercion to same type before comparison)
=== checks type as well as value - strict equality
(also used for strings)

Question 10

What properties does the keyword “let” have in JS?

Answer 10

• to introduce a declaration

- smallest scope (block scope { } )

Question 11

What properties does the keyword “var” have in JS?

Answer 11

• to introduce a declaration

- global/function scope

Question 12

What properties does the keyword “const” have in JS?

Answer 12

• to introduce a declaration
• block scope { }
• cannot be updated - like final in Java

Question 13

How are variables declared if let, var and const are NOT used?

Answer 13

Variable will be globally scoped

Question 14

List 4 objects that are accessible via the JS DOM API

Answer 14

• document
• window
• navigator
• screen

Question 15

Where in HTML should a script tag for JS be placed?

Answer 15

At the bottom of the page (just before