Trivia

Question 1

Define hoisting.

Answer 1

when declared variables have their declaration “moved up” to top of the current scope

Question 2

Explain Event Delegation.

Answer 2

technique involving adding event listeners to a parent element instead to descendant elements.

Question 3

Describe Closure.

Answer 3

feature where an inner function has access to the outer enclosing function’s variables.
(Scope Chain)

Question 4

Explain how “this” in Javascript works.

Answer 4

• the object that “this” refers changes every time execution context is changed
• refers to the object depending which scope

Question 5

Differences between let, var and const?

Answer 5

• var: can be updated or redeclared within scope
• let: can be updated but NOT redeclared
• const: CANNOT be updated and CANNOT be redeclared
• let and const are BLOCKED scope whereas var is globally scoped

Question 6

What is TCP?

Answer 6

Transmission Control Protocol

• CONNECTION ORIENTED
• once connection established, data can be sent bidirectional

Question 7

What is UDP?

Answer 7

User Datagram Protocol

• CONNECTIONLESS Internet Protocol
• multiple messages can be sent as packets in chunks using UDP

Question 8

Prototypal Inheritance:
- All JS objects have a 1 property that is reference to another 2.
- When property accessed on an object, and if not found on that object, the JS engine looks at object’s 3, and so on until end of prototype chain.
This stimulates 4 inheritance, but really more of 5 inheritance.

Answer 8

1. ) prototype
2. ) object
3. ) prototype
4. ) classical
5. ) delegation

Question 9

Define Promise.

Answer 9

An object may produce a single value some time in the future: either a resolved value, or a reason that it is not resolved.

Question 10

Describe Event Bubbling.

Answer 10

When an event triggers on the DOM element, it will attempt to handle the event if there’s a listener attached, then the event is bubbled up to its parent and the same thing happens.
This bubbling occurs up the element’s ancestors all the way up to the document.

Question 11

Describe Load Balancer.

Answer 11

It helps spread traffic across cluster of servers to improve app/site/db.
Can add between client-server, and server-db.

Question 12

What are CSS preprocessors? Give example(s) and give pros and cons.

Answer 12

A css preprocessor is a program that generate CSS from preprocessors’s own unique syntax.

• ex: Sass and LESS
• Pro: allows you to reuse pieces of code that you’ve already written
  
  • more organized
• Con: longer to debug
  
  • time-consuming to compile
  • performance may be compromised

Question 13

Can you name 2 programming paradigms important for JS app developers?

Answer 13

Javascript is a multi-paradigm language, supporting imperative/procedural programming along with OOP and functional programming. JS supports OOP with prototypal inheritance.

Question 14

What is functional programming?

Answer 14

type of language that avoids shared state and mutable data.

- pure functions used, avoiding side-effects

Question 15

Define CORS

Answer 15

Cross-Origin Resource Sharing
allows restricted resources (eg. fonts) on a web page to be requested from another domain outside the domain from which the resource originated

Question 16

What are Websockets?

Answer 16

Protocol providing communication channels over a single TCP connection