ES6

Question 1

What is a code block?

What are some examples of a code block?

Answer 1

• Chunk of code within curly braces

- if statements, loops, functions

Question 2

What does scope mean?

Answer 2

It’s not available outside of the code block that it’s currently inside of

Question 3

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

Answer 3

Block-scope

var is a function-scope

Question 4

What is the difference between let and const?

Answer 4

• let can be updated but not re-declared

- const cannot be updated OR redeclared

Question 5

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

Answer 5

Because it’s data in a reference – not the variable itself

Question 6

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

Answer 6

If you know that your value will never change, use const – otherwise use let

Question 7

What is the syntax for writing a template literal?

Answer 7

` ${ } `

Question 8

What is “string interpolation”?

Answer 8

Embedding variables and expressions in a string

Question 9

What is destructuring, conceptually?

Answer 9

o Extracting data from objects and arrays

o Taking objects and arrays and converting them into smaller objects, arrays, variables

Question 10

What is the syntax for Object destructuring?

Answer 10

let { property1: variable1, propeprty2: variable2 } = objectName;

Question 11

What is the syntax for Array destructuring?

Answer 11

let [x, y, z] = variableName

Question 12

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

Answer 12

var/let/const followed by {} or []

Question 13

What is the syntax for defining an arrow function?

Answer 13

o Parameter => expression
o (parameter1, parameter) => expression

Note: Parentheses for parameters are needed only when there are >1 parameters

Question 14

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

Answer 14

Implicit return (It implies that you want to return)

Note: When you have curly braces, you have to explicitly write ‘return’

Question 15

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

Answer 15

When the function is being defined (at definition time)

Question 16

What are the three states a Promise can be in?

Answer 16

pending
fulfilled
rejected

Question 17

How do you handle the fulfillment of a Promise?

Answer 17

.then( )

Question 18

How do you handle the rejection of a Promise?

Answer 18

.catch( )

Question 19

What is “syntactic sugar”?

Answer 19

Syntax in a programming language that allows humans to make their code easier to read/write

Question 20

what is the ‘typeof’ n ES6 class?

Answer 20

function

Question 21

Describe ES6 class syntax?

Answer 21

class Name {

OPTIONAL
constructor(parameter1, …parameters) {
code;
}

OPTIONAL
functionName( ) {
code;
}

};

Question 22

What is refactoring?

Answer 22

Process of restructuring existing code but the behavior remains the same