ES 6

Question 1

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

Answer 1

Code block is pair of curly braces used to group zero or more statements. Some examples are if else statements, for loops, do while, while loops

Question 2

What does block scope mean?

Answer 2

variables only exist within corresponding code block.

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

the blocked scoped variables declared using const cannot be reassigned. Let can be reassigned.

Question 5

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

Answer 5

We cannot reassign the variable to another array but const still allows values of the array to be changed.

Question 6

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

Answer 6

always use const. If const cannot be used, use let.

Question 7

What is the syntax for writing a template literal?

Answer 7

back tick, dollar sign, curly braces ${}

Question 8

What is “string interpolation”?

Answer 8

String formatting: the ability to substitute part of the string for the values of variables or expressions. This feature is also called string interpolation.

Question 9

What is destructuring, conceptually?

Answer 9

The destructuring assignment syntax is a JavaScript expression that makes it possible to unpack values from arrays, or properties from objects, into distinct variables

Question 10

What is the syntax for Object destructuring?

Answer 10

declaration, curly braces, property name.

let { firstName: fname, lastName: lname } = person;

Question 11

What is the syntax for Array destructuring?

Answer 11

declaration, square brackets, property name.

let [x, y, z] = getScores();

Question 12

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

Answer 12

instead of values being pulled out of an array, properties (keys) and their values can be pulled out of an object. Object we use curly braces and arrays we use square brackets.

Question 13

What is the syntax for defining an arrow function?

Answer 13

let add = (x, y) => x + y;

Question 14

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

Answer 14

if you use the block syntax, you need to specify the return keyword, if not we do not need the return keyword. (no curly braces = implicit return

Question 15

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

Answer 15

an arrow function captures the this value of the enclosing context instead of creating its own this context.

Question 16

What are the three states a Promise can be in?

Answer 16

fulfilled, rejected, or pending

Question 17

How do you handle the fulfillment of a Promise?

Answer 17

.then method

Question 18

How do you handle the rejection of a Promise?

Answer 18

.catch method

Question 19

What is “syntactic sugar”?

Answer 19

In computer science, syntactic sugar is syntax within a programming language that is designed to make things easier to read or to express. It makes the language “sweeter” for human use: things can be expressed more clearly, more concisely, or in an alternative style that some may prefer.

Question 20

What is the typeof an ES6 class?

Answer 20

function

Question 21

Describe ES6 class syntax.

Answer 21

class ClassName {
  constructor() { ... }
}

Question 22

How are ES Modules different from CommonJS modules?

Answer 22

While CommonJS and ES6 modules share similar syntax, they work in fundamentally different ways: ES6 modules are pre-parsed in order to resolve further imports before code is executed. CommonJS modules load dependencies on demand while executing the code. we use import and export instead of module.exports and require.

Question 23

What kind of modules can Webpack support?

Answer 23

Webpack supports the following module types natively: ECMAScript modules. CommonJS modules. ES6, and AMD modules.