es6

Question 1

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

Answer 1

an area within curly braces with the exception of a for loop. Some examples are functions definitions and for loops.

Question 2

What does block scope mean?

Answer 2

if it’s inside the code block it stays in the code block.

Question 3

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

Answer 3

block scoped which means they stay within the code block.

Question 4

What is the difference between let and const?

Answer 4

let can be reassigned and const cannot be reassigned.

Question 5

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

Answer 5

you are not re-assigning the array itself, but instead adding to it.

Question 6

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

Answer 6

use const and let the compiler tell you if you are unsure which declaration to use. If it is gonna be reassigned use let if not use const.

Question 7

What is the syntax for writing a template literal?

Answer 7

backticks and $ and curly braces for substitutions.

Question 8

What is “string interpolation”?

Answer 8

The substitutions allow you to embed variables and expressions in a string. The JavaScript engine will automatically replace these variables and expressions with their values.

Question 9

What is destructuring, conceptually?

Answer 9

taking parts of it out and re-assigning them

Question 10

What is the syntax for Object destructuring?

Answer 10

keyword const or let, curly braces, property name, =, and name of original object

Question 11

What is the syntax for Array destructuring?

Answer 11

keyword const or let, square bracket, name of element at index, =, name of original array

Question 12

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

Answer 12

which side the equal sign is on the variable name. Left side is destructuring and right side is creating.

Question 13

What is the syntax for defining an arrow function?

Answer 13

() => with or without curly braces

Question 14

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

Answer 14

returns the expressions without curly braces only one expression is returned

Question 15

What are the three states a Promise can be in?

Question 16

How do you handle the fulfillment of a Promise?

Answer 16

Promise.then()

Question 17

How do you handle the rejection of a Promise?

Answer 17

Promise.catch()

Question 18

What are JavaScript classes?

Answer 18

template for

Question 19

When would you want to use a class?

Answer 19

so you can encapsulate all the functionality in one place

Question 20

How do you declare a class?

Question 21

How do you inherit from another class?

Question 22

Why would you want to inherit from another class?

Answer 22

to keep the object and all its methods relatively small also for reusability

Question 23

How do you add methods and properties to a class?

Answer 23

add the method in the code block