ES6

Question 1

What is a code block? What are some examples of a code block?

Answer 1

Code blocks are indicated by curly braces and it helps to declare data as local

Question 2

What does block scope mean?

Answer 2

Does not create property on global window object. Declaring a variable inside any code block shown by curly brackets and only lives and acts inside.

Question 3

What is the scope of a variable declared with const or let?

Answer 3

They are blocked-scope compared to var which is global scope or local scope

Question 4

What is the difference between let and const?

Answer 4

const cannot be reassigned and variable reference cannot change while let can be. Therefore, const needs to be always assigned a value when declared

Question 5

Why is it possible to .push() a new value into a const variable that points to an Array?

Answer 5

You could update the values but cannot change the reference points

Question 6

How should you decide on which type of declaration to use?

Answer 6

If you want to reassign variables then use let and if variables don’t need to be changed but just the value you can use const

Question 7

What is the syntax for writing a template literal?

Answer 7

` string content ` - use back-ticks instead of quotes and to substitute a variable and an expression: ${variableName}

Question 8

What is “string interpolation”?

Answer 8

the ability to substitute part of the string for the values of variables or expressions

Question 9

What is destructuring, conceptually?

Answer 9

unpacking values and assigning variables

Question 10

What is the syntax for Object destrucuring?

Answer 10

const {property1: variable1, property2: variable2} = object;

Question 11

What is the syntax for Array destructuring?

Answer 11

const/let [variable1, variable2, variable3] = array

Question 12

How can you tell the difference between destructuring and creating Object/Array literals?

Answer 12

Destructuring - you’re not adding any new values to the object or an array and whether assigned variables to existing object/array literals. Destructuring also have brackets go on the lefthand side while creating is on the righthand side.

Question 13

What is the syntax for defining an arrow function?

Answer 13

const variable = (x,y) => return statement

Question 14

When an arrow function’s body is left without curly braces, what changes in its functionality?

Answer 14

No curly braces will result in implicit return

Question 15

How is the value of this determined within an arrow function?

Answer 15

normal this is determined by calltime, but in arrow function you look at where the function is defined or definition time

Question 16

What are the three states a Promise can be in?

Answer 16

fulfilled: meaning that the operation was completely successful, rejected: meaning that the operation failed, pending: initial state, neither fulfilled nor rejected

Question 17

How do you handle the fulfillment of a Promise?

Answer 17

promise.prototype.then()

Question 18

How do you handle the rejection of a Promise?

Answer 18

promise.prototype.catch() or optional second function on then()

Question 19

What is “syntactic sugar”?

Answer 19

syntax that simplifies reading and expressing - it makes the language “sweeter” for human use

Question 20

What is the typeof an ES6 class?

Answer 20

functions

Question 21

Describe ES6 class syntax.

Answer 21

class keyword with ObjectName { } - inside the curly braces we use constructor() which is where you can initialize the properties of an instance

Question 22

What is “refactoring”?

Answer 22

Process of restructuring existing computer code without changing the behavior

Question 23

How are ES Modules different from CommonJS modules?

Answer 23

ES Modules have different syntax and commonJS is part of node rather than

Question 24

What kind of modules can Webpack support?

Answer 24

ECMAScript modules. CommonJS modules. AMD modules, etc