es6

Question 1

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

Answer 1

code wrapped in curly braces ({}). if, if else, while, etc.

Question 2

What does block scope mean?

Answer 2

Only accessible inside of the code block.

Question 3

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

Answer 3

block scope

Question 4

What is the difference between let and const?

Answer 4

A constant variable cannot be reassigned. let variables 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 value inside the array is not immuatable

Question 6

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

Answer 6

Use let const unless you cant, then use let

Question 7

What is destructuring, conceptually?

Answer 7

Assigning properties of an object or elements of an array to individual variables

Question 8

What is the syntax for Object destructuring?

Answer 8

const/let {} = obj

Question 9

What is the syntax for Array destructuring?

Answer 9

const let [] = obj

Question 10

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

Answer 10

an object literal / array literal is assigned to a variable in creation. In destructuring, the name of the created object/array is assigned to an object/array containing the variables.

Question 11

What is the syntax for writing a template literal?

Answer 11

` ` and use ${} for string interpolation

Question 12

What is “string interpolation”?

Answer 12

the ability to substitute part of the string for the values of variables or expressions

Question 13

What is the syntax for defining an arrow function?

Answer 13

functionName = (parameters) => {expression}.

Question 14

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

Answer 14

Curly braces are not needed unless there is a statement being used

Question 15

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

Answer 15

By where it is defined, not by who calls it

Question 16

What are the three states a Promise can be in?

Answer 16

pending: initial state, neither fulfilled nor rejected.
fulfilled: meaning that the operation was completed successfully.
rejected: meaning that the operation failed.

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

syntax within a programming language that is designed to make things easier to read or to express.

Question 20

What is the typeof an ES6 class?

Answer 20

function

Question 21

Describe ES6 class syntax.

Answer 21

class Animal {
    constructor(type) {
        this.type = type;
    }
    identify() {
        console.log(this.type);
    }
}

Question 22

What is “refactoring”?

Answer 22

the process of restructuring existing computer code—changing the factoring—without changing its external behavior

Question 23

How are ES Modules different from CommonJS modules?

Answer 23

Their syntax is even more compact than CommonJS’s.
Their structure can be statically analyzed (for static checking, optimization, etc.).
Their support for cyclic dependencies is better than CommonJS’s.

Question 24

What kind of modules can Webpack support?

Answer 24

ECMAScript modules
CommonJS modules
AMD modules
Assets
WebAssembly modules