ES6

Question 1

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

Answer 1

statements inside curly brackets

statements inside of functions, conditionals or loops

Question 2

What does the block scope mean?

Answer 2

area within conditionals or loops

something that only exists within the corresponding block

Question 3

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

Answer 3

block-scope

Question 4

What is the difference between let and const?

Answer 4

et can be reassigned, const cannot

Question 5

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

Answer 5

you can change the elements inside of the array, but cannot reassign that array to another array

Question 6

How should you decide which type of declaration to use?

Answer 6

should use const for anything that will be a constant variable. anything that will need to be reassigned should be let

Question 7

What is the syntax for writing a template literal?

Answer 7

wrapping your text in backticks accounting for whitespace

Question 8

What is string interpolation?

Answer 8

the ability to substitute part of the string for the values of variables or expressions
the javascript engine will automatically replace these variables and expressions by their values

Question 9

What is destructuring conceptually?

Answer 9

an expression that makes it possible to unpack values from arrays or properties from objects, into distinct variables

Question 10

What is the syntax for Object destructuring?

Answer 10

var, const or let keyword followed by curly braces and the properties you want assigned separated by a colon from the names of the variables you want them assigned to and the object name at the end following the closing curly brace and assignment operator

Question 11

What is the syntax for Array destructuring?

Answer 11

var, const or let keyword followed by brackets and the variable names you want assigned in the order of the indexes you want assigned to them and the array literal name at the end following the closing bracket and assignment operator

Question 12

How can you tell the difference between destructuring and creating object/array literals?

Answer 12

object/array name is always at the end when destructuring following the closing curly brace/bracket and the assignment operator

Question 13

What is the syntax for defining an arrow function?

Answer 13

remove the function keyword.
parameters are listed (if more than one, listen within parentheses) followed by function arrow
multiline statements require body brackets and return

Question 14

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

Answer 14

you can use an expression without curly braces but not a statement

Question 15

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

Answer 15

arrow functions establish this based on the scope the arrow function is defined within
in regular functions the this keyword represented the object that called the function, which could be the window, the document, a button, etc
with arrow functions, this always represents the object that defined the arrow function

Question 16

What is Array.prototype.filter useful for?

Answer 16

allows you to create a new array with all elements that pass a test that you implement
creates a new array while excluding some elements

Question 17

What is Array.prototype.map useful for?

Answer 17

when you want to transform the each element of an array

Question 18

What is Array.prototype.reduce useful for?

Answer 18

combining the elements of an array into a single value

Question 19

What is syntactic sugar?

Answer 19

syntax within a programming language that is designed to make things easier to read or to express

Question 20

What is the typeof an ES6 class?

Answer 20

function

Question 21

Describe ES6 class syntax.

Answer 21

class keyword followed by name with first letter capitalized
curly brace for class declaration
constructor function with parameters

Question 22

What is refactoring?

Answer 22

process of restructuring existing computer code - changing the factoring - without changing its external behavior.

Question 23

How are ES Modules different from CommonJS Modules?

Answer 23

more compact syntax
structure can be statically analyzed
support for cyclic dependencies is better than CommonJS

Question 24

What kind of modules can Webpack Support?

Answer 24

ECMAScript Modules
CommonJS modules
AMD modules
Assets
WebAssembly Modules
modules written via loaders
dependency modules