ES6

Question 1

What is Babel?

Answer 1

(The most popular es6 transpiler)

• Transpiles es6 into the supported pre-es6 JS so browsers can read the newer version.

Question 2

What is a “transpiler”?

Answer 2

A transpiler reads code written in one language and produces the equivalent code in another.

Question 3

Why do we need transpilers?

Answer 3

• We need transpilers so that our pretty es6 code compiles into the dense JavaScript code that browser like.
• Browsers only currently have widespread support of older JS
• Transpilers convert advanced TypeScript and CoffeeScript code back into the original JS

Question 4

Benefits of webpack

Answer 4

Using webpack allows us to create an environment that transforms es6 code with babel.
• It combines multiple modules into one js file to reduce errors and resources on the client-side.
• Shipping with a development server, it gives us live code updating for free!

Question 5

What is weppack

Answer 5

Webpack is an open-source JavaScript module bundler. It is a module bundler primarily for JavaScript, but it can transform front-end assets like HTML, CSS, even images if the corresponding plugins are included.

Question 6

{variable name} some words

Answer 6

template literals

Question 7

{…variable name}. Inserts the content of one variable into another variable by inserting …variableName

Answer 7

Spread Operator

Question 8

The ‘var’ keyword allows for block scoping?

Answer 8

False. It does not allow block scoping. Re-using the same variable with ‘var’ twice in coding blocks will overwrite data.

Question 9

Which es6 keyword declares a variable that cannot be re-assigned or re-declared?

Answer 9

const

Question 10

___ replaces var in es6 in term of variable assignment.

Answer 10

let

Question 11

T or F: “let” allows for block scoping.

Answer 11

True

Question 12

T or F: “const” allows for block scoping

Answer 12

True

Question 13

_____ scope refers to the set of statements, variables, objects, and more that confine to a coding block denoted by a pair of curly braces: {…}

Answer 13

Local

Question 14

____ scope refers to the set of statements, variables, objects, methods, and more that exist outside and beyond all local scope functions and coding blocks.

Answer 14

Global

Question 15

____ ______ allow for the gathering of multiple parameter calls into one array: Denoted by three periods.

Answer 15

Rest parameter

Question 16

Destructuring assignment on arrays allows for much more efficient array manipulation and assigns multiple variables from array data based on the index value.

Answer 16

just remember

Question 17

Destructuring assignment on objects allows for more concise object manipulation and assigns multiple variables from object data based on keynames.

Answer 17

just remember

Question 18

By default, _____ functions are anonymous.

Answer 18

anonymous

Question 19

() => {} : This syntax is…

Answer 19

an arrow function

Question 20

The ____ _____ creates new arrays by calling a function on individual

Answer 20

map method

Question 21

The ____ _____ creates new arrays based on an original array and a certain test on each of its element.

Answer 21

filter method

Question 22

The most common ways you’ll see arrow functions show up in es6 code is with _____ methods.

Answer 22

helper

Question 23

What are modules?

Answer 23

Split code into unique files baed on relevant data.

Enables us to split our code into files based on relevant information.

Question 24

We handle modules in es6 with the _____ and _____ keywords.

Answer 24

import and export

Question 25

_____ keyword sends data to other modules

Answer 25

export

Question 26

What are anonymous function expressions?

Answer 26

Function expressions that don't explicitly assign a name to the function like a function declaration does.

Question 27

Change the code below to an arrow function: setTimeout (function() { console.log("Woohoo!"); }, 3000);

Answer 27

setTimeout (() => { console.log("Woohoo!"); }, 3000);

Question 28

Change the code below to a string literal template: let b = "wooh" + "oo".repeat(50) + "oo"; console.log(b);

Answer 28

``` let b =`wooh${"oo.repeat(50)}`; console.log(b); ```

Question 29

T or F: Arrow functions are anonymous by default

Answer 29

True. Anonymous functions are always anonymous because they do not use the 'function declaration.

Question 30

T or F: Which es6 helper method allows us to create arrays by calling a specific function on each element within an initial array?

Answer 30

map method

Question 31

Which built-in helper method could I use to check if a number is a not greater than 2^53 in JavaScript?

Answer 31

Number.isSafeInteger()

Question 32

Classes in JavaScript are defined with the ____ keyword and uses a ______.

Answer 32

class. constructor

Question 33

Classes in JavaScript relate to each other through ______.

Answer 33

inheritance

Question 34

Classes in JavaScript use the ____ keyword to create child classes.

Answer 34

extends

Question 35

What is Object-Oriented Programming?

Answer 35

Objects or classes hold relevant data that interact with each other.

Question 36

Is JavaScript based on object-oriented programming or prototype inheritance model?

Answer 36

Prototype inheritance model

Question 37

Classes are _______ on top of JavaScript prototypes.

Answer 37

extractions

Question 38

A prototype reveals an object's _______.

Answer 38

parent

Question 39

All objects - Arrays, Dates, etc.. have a ______.

Answer 39

prototype

Question 40

T or F: Objects (including arrays and functions) assigned to a variable using const are mutable.

Answer 40

True

Question 41

higher order functions, such as map(), filter(), and reduce(), take other functions as arguments for processing ______________.

Answer 41

collections of data.

Question 42

With the ____ operator, you can create functions that take a variable number of arguments. These arguments are stored in an array that can be accessed later from inside the function.

Answer 42

rest

Question 43

The _______ keyword initializes an object for class.

Answer 43

constructor

Question 44

The _____ keyword creates subclasses and children of parent classes.

Answer 44

extends

Question 45

T or F: Static methods in classes can be called even outside the context of class.

Answer 45

True

Question 46

JavaScript is not based on object-oriented programming, but a _____-_______ model

Answer 46

prototypal-inheritance

Question 47

A _________ is a characteristic in every JavaScript object that reveals its parent and the properties that it inherits.

Answer 47

prototype

Question 48

All JavaScript _____ contain a prototype and can trace their chain of prototypal inheritance all the way back to the base level Object prototype.

Answer 48

objects

Question 49

Arrow functions don’t create their own local ‘this’ object like a normal function prototype, but instead refer to the ‘this’ tied to its _____ scope.

Answer 49

outer

Question 50

classes are simply ___1___, and ____1____ are simply references to an object’s parent.

Answer 50

prototypes,

Question 51

classes are simply prototypes, and prototypes are simply references to an object’s ______.

Answer 51

parent

Question 52

Data structures in computer science refer to...

Answer 52

the programming storage of data for efficient usage in applications and algorithms.

Question 53

A Set compares to a more advanced array that has all ____ elements and no _____ values.

Answer 53

unique, duplicate

Question 54

Set iteration frequently occurs through the _____ helper method.

Answer 54

values()

Question 55

A ____ represents a more advanced object in es6 with key-value pairs that can have non-string keys.

Answer 55

Map

Question 56

Map() is an alternative to using _____ _____ for storing key/value pairs that requires unique keys.

Answer 56

object literals

Question 57

How do you create a new Map?

Answer 57

new Map([iterable: can be an array or any iterable object whose elements are key/value pairs]).

Question 58

Map iterate frequently occurs through the ______ helper method.

Answer 58

entries()

Question 59

Closures

Answer 59

Functions that remember the environment that they were created in and could further reference the independent variables within that environment.

Question 60

Function Factories

Answer 60

Functions that return other functions to make more adaptable methods.

Question 61

ES6 Generators

Answer 61

Breaks the typical "run to completion" model for functions. • Whenever we run a function we expected to complete before moving on in the program, therefore other expressions and statements can only happen once the function has finished. Generators can pause and resume a function, with yield() and next()

Question 62

what is an iterator?

Answer 62

Accesses items from a collection or array one at a time and it keeps track of its position as it does so.

Question 63

Es6 generators have a ____, ____, and ____ functionality.

Answer 63

start, pause, and reset

Question 64

Do generators follow the typical "run to completion" model of normal functions?

Answer 64

No. Generators break the "run to completion" model and introduce functions that can start, pause, and reset!

Question 65

Which of the following lines demonstrates a proper instance of a generator? a. const gen = new generator(); b. const gen = generator();

Answer 65

b. const gen = generator(); Generators actually do not use the 'new' keyword to instantiate.

Question 66

Which keyword is used within a generator to tell it to 'pause'?

Answer 66

yield

Question 67

What is the syntax for a generator?

Answer 67

Generators use the syntax of a normal function, but have an asterisk following the function keyword: function* generator { … } .

Question 68

The generator ____ keyword signals when to ‘pause’ the function and return its current state.

Answer 68

yield

Question 69

Generator instances don’t use the ____ keyword like the typical function prototype or Object.

Answer 69

new

Question 70

Using the generator’s special ____ method allows us to access its yielded state.

Answer 70

next()

Question 71

Passing values to the ____ method introduces a way for generators to reset, or complete their runtime.

Answer 71

next()

Question 72

An ______ in JavaScript demonstrates a type of object that can access values in a collection one at a time.

Answer 72

iterator

Question 73

Why are generators so useful?

Answer 73

Because they introduce a lot of control in flow of functions.