JavaScript ES6

Question 1

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

Answer 1

block

Question 2

Name some characteristics of a variable declared using const.

Answer 2

Preferred method,
Value of variable cannot be reassigned
Declares constants (immutable)
Not hoisted

Question 3

Name some characteristics of a variable declared using let.

Answer 3

Value of variable can be changed (mutable)
Must use let in for loops
Not hoisted

Question 4

What does block scope mean?

Answer 4

Only can be accessed inside the block of code declared/initialized and children scopes

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

The binding or association between variable name and variable value (const x = []) is immutable, but the items at the indexes are mutable 
**Modifying the reference data type stored in memory

Question 6

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

Answer 6

Cannot be access in the global Object (window)
Hoisted
can be redeclared, reassigned

Question 7

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

Answer 7

Easy to make mistakes and reassign variables

Question 8

What is the syntax in writing a template literal?

Answer 8

` text goes ${javascript } here`

Question 9

What is string interpolation?

Answer 9

if you put a dynamically computed value inside a ${}, it is converted to a string and inserted into the string returned by the literal.
**Inject javascript into a string

Question 10

When was destructuring introduced?

Answer 10

ES6 (2015)

Question 11

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

Answer 11

Might miscount the number of commas or miss some

Large arrays

Question 12

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

Answer 12

assignment and {} happens on the left side of the colon

Question 13

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

Answer 13

ES6 - ‘this’, arguments, new.target, super have lexical scope and less wordy (don’t need function keyword)
binding won’t work

Question 14

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

Answer 14

In methods and constructors, not want to utilize lexical this

Question 15

Lexical scope

Answer 15

Inherit’s parent’s this

Question 16

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

Answer 16

one line statements will be implicitly returned

Question 17

In what situations would you possibly use an arrow function?

Answer 17

Callbacks, one line statements, lexical this