ES6

Question 1

Variables defined with the var keyword are function scoped. const and let are _____ scoped.

Answer 1

block-scoped

Question 2

Name some characteristics of a variable declared using const.

Answer 2

it is immutable, the value cannot be changed,
however properties can be assigned to it,
must initialize immediately

Question 3

Name some characteristics of a variable declared using let.

Answer 3

mutable, value can be changed, and it does not have to be initialized

Question 4

What does block scope mean?

Answer 4

its scope is defined by the curly braces it is contained in

Question 5

In the file we can push a new value to an array defined using the const variable. How does that work?

Answer 5

it is a reference to the location in memory

Question 6

Name some things that var can do that const and let can’t.

Answer 6

they are accessible outside of their blocks, can be hoisted, var can be redeclared, and redefined

Question 7

If var can be used virtually anywhere, why would we switch?

Answer 7

minimize the errors that var can cause,

and to have absolute control over the variables being used , (ie no auto global variables)

Question 8

What is the syntax in writing a template literal?

Answer 8

use the grave markers ` and then javascript expression ${}

${example}

Question 9

What is string interpolation?

Answer 9

allows us to perform javascript expressions within strings

Question 10

When was destructuring introduced?

Answer 10

2015 ES6

Question 11

Why could the running commas technique of destructuring an array be a bad idea?

Answer 11

If an array is very large, you need a lot of commas; if so, just grab the value the normal way

Question 12

How can you easily tell the difference between destructuring and creating array/object literals.

Answer 12

curly braces are on the left side of the equal sign

Question 13

How does an ES6 arrow function differ from an ES5 function?

Answer 13

arrow functions dont need to be bound, and they are determined by lexical scope

Question 14

When an arrow function’s code block is left without curly braces, what (if anything) changes in its functionality?

Answer 14

without curly braces, the code to the right of arrow will be implicitly returned

Question 15

In what situations would you possibly use an arrow function?

Answer 15

callback functions where “this” will have a different value from its normal scope.

Question 16

In what situations would you not want to use an arrow function?

Answer 16

when you dont want it to use lexical this