es6

Question 1

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

Answer 1

Code blocks are chunks of code within two curly brackets { }

Many things use { }, such as loops, if else statements, etc

Question 2

What does block scope mean?

Answer 2

The value exists within the scope of the code block

Afterward, the value is returned to its original value

Question 3

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

Answer 3

block-scoped

Question 4

What is the difference between let and const?

Answer 4

let allows you to change the value of a variable within a code block

const keeps the value and the it can never be changed
Unless it is referring to properties inside of an object

Question 5

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

Answer 5

You can edit the items inside a const array. But the object itself, can never not be an array

We are not changing the name binding. We are not changing where the items points

Question 6

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

Answer 6

const should be used for items that will not be edited later

let is used when you know you will be changing the value of an item later on

Question 7

What is the syntax for writing a template literal?

Answer 7

const bio = My name is ${firstName} ${lastName} and I am ${age} years old.;

Question 8

What is “string interpolation”?

Answer 8

Defining a string using template literal and plugging in javascript expressions ( ${ } )

The ability to embed variables and expressions into a string you would concatenated

Question 9

What is destructuring, conceptually?

Answer 9

Being able to pull the values of an object or array, in such a way that would now require us to refer to the data’s container later on.

Question 10

What is the syntax for Object destructuring?

Answer 10

First you have the object literal:
const book1 = {
      title: 'Goodnight Punpun',
      author: 'Inio Asano',
      libraryID: 3353
    };

Then you can deconstruct the object:
const { title, author, libraryID } = book1;

You can now use the values freely:
console.log(The title of this book is ${title}, the author is ${author}, and the library id is ${libraryID});

Question 11

What is the syntax for Array destructuring?

Answer 11

You have your regular array:
const numbers = ['one', 'two', 'three', 'four'];

You deconstruct it:
const [first, second, …remainder] = numbers;

Use each of those elements freely:

console. log(first); // “one”
console. log(second); // “two”
console. log(remainder); //this will console [“three”, “four”]

Question 12

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

Answer 12

When creating objects/arrays, the name of the object is on the left side of the = sign:

const book1 = {title: 'Goodnight Punpun', author: 'Inio Asano', libraryID: 335 };
const numbers = ['one', 'two', 'three', 'four'];

When deconstructing them, the properties or list are on the left side of the = sign:

const { title, author, libraryID } = book1;
const [first, second, …remainder] = numbers;

Question 13

What is the syntax for defining an arrow function?

Answer 13

let functionName = (argument1, argumentN) => { return stuff; }

Question 14

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

Answer 14

Leaving out the curly braces, means you have an implied “return”

As soon as you include curly braces, you need to add “return”

Question 15

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

Answer 15

The value of THIS is determined at definition time, not call time

In other words, it doesn’t have it’s own THIS, but gets the THIS location of the function it is being called from (aka the object containing the method, which uses the method)