ES6

Question 1

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

Answer 1

section of code enclosed within { }, ex: function, conditional, loop

Question 2

What does block scope mean?

Answer 2

a value is only available within a certain code 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

let variables can be reassigned, const variables can’t

Question 5

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

Answer 5

you can’t reassign a const variable, but you can change the value of the variable

Question 6

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

Answer 6

if a variable needs to be a reassigned, use let, otherwise use const

Question 7

What is the syntax for writing a template literal?

Answer 7

Use backticks instead of quotes

Question 8

What is “string interpolation”?

Answer 8

replacing substitutions with the values of the variables and expressions

Question 9

What is destructuring, conceptually?

Answer 9

taking apart an object or array and assigning the parts to different variables

Question 10

What is the syntax for Object destructuring?

Answer 10

let { prop1: var1, prop2: var2} = object;

Question 11

What is the syntax for Array destructuring?

Answer 11

let [ x, y, z ] = array;

Question 12

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

Answer 12

it’s destructuring if the brackets are on the left of the assignment operator, creating if the brackets are on the right

Question 13

What is the syntax for defining an arrow function?

Answer 13

( parameters ) => {statements};

Question 14

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

Answer 14

without the curly braces, you can only have one expression

Question 15

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

Answer 15

the value of this is determined by the value of this in its containing code block

Question 16

What are the three states a Promise can be in?

Answer 16

pending (initial state), fulfilled (success), rejected (fail)

Question 17

How do you handle the fulfillment of a Promise?

Answer 17

.then ( onFulfilled, onRejected )

Question 18

How do you handle the rejection of a Promise?

Answer 18

.catch ( onRejected )

Question 19

What is “syntactic sugar”?

Answer 19

syntax that makes things easier to read or express

Question 20

What is the typeof an ES6 class?

Answer 20

function

Question 21

Describe ES6 class syntax.

Answer 21

class keyword ClassName {
   constructor(params) {
      this.prop = param;
      }
   functionName( ) {
      return this.prop;
   }
}

Question 22

What is “refactoring”?

Answer 22

restructuring code without changing functionality to improve design + structure

Question 23

How are ES Modules different from CommonJS modules?

Answer 23

syntax

Question 24

What kind of modules can Webpack support?

Answer 24

CommonJS, ESM, AMD, Assets, WebAssembly