es6

Question 1

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

Answer 1

a section of code located within a set of curly braces.

Ex. if else, for, do while, while, etc.

Question 2

What does block scope mean?

Answer 2

If a block-scoped variable is declared within a code block, that variable’s value will only be accessible within that code block.

Question 3

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

Answer 3

block-scoped

var is function-scoped

Question 4

What is the difference between let and const?

Answer 4

const is read-only and cannot be reassigned. let values 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

The array itself is being modified, but the variable name is still pointing to the same array

Question 6

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

Answer 6

Whether a variable’s value will need to be changed or not. If it needs to be changed, then let is needed. If the variable value will not change, then const is needed.

Question 7

What is the syntax for writing a template literal?

Answer 7

Backticks instead of quotes, ${ } for variables/expressions

Question 8

What is “string interpolation”?

Answer 8

substituting part of the string for the values of variables or expressions

Question 9

What is destructuring, conceptually?

Answer 9

A syntax that provides an alternative way to assign properties of an object to variables

Question 10

What is the syntax for Object destructuring?

Answer 10

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

let { firstName, lastName } = person;

Question 11

What is the syntax for Array destructuring?

Answer 11

let [x, y, z] = arrayName;

Question 12

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

Answer 12

The name of the Object/Array literal is on the left side of the assignment operator when creating, and it’s on the right side when destructuring.

Question 13

What is the syntax for defining an arrow function?

Answer 13

( ) => {

}

Question 14

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

Answer 14

The result of the expression will be returned

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

pending, fulfilled, rejected

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

A shorter syntax within a programming language that reduces how much code is needed to perform an operation, and improves readability of said code

Question 20

What is the typeof an ES6 class?

Answer 20

function

Question 21

Describe ES6 class syntax.

Answer 21

class ClassName {
  constructor(property) {
    this.property = property;
  }
  method() {
    code block
  }

Question 22

What is “refactoring”?

Answer 22

Simplifying written code to make it shorter and more readable while maintaining the intended function of the original code

Question 23

How are ES Modules different from CommonJS modules?

Answer 23

Different syntax (import / export), asynchronous loading, browser use

Question 24

What kind of modules can Webpack support?

Answer 24

ECMAScript modules. CommonJS modules. AMD modules