Fundamentals

Question 1

What are the 8 main data types?

Answer 1

String, number, bigint, array, object, symbol, null, undefined

Question 2

What is the difference between null and undefined?

Answer 2

undefined is given to variables not yet given a value, while null is a value that can indicate data missingness.

Question 3

What values are “Falsy”?

Answer 3

“”
NaN
undefined
null
0

Question 4

What does a NaN value represent?

Answer 4

Not a Number. A result of an invalid mathematical expression, like 5/“apple”

Question 5

What values are “truthy”?

Answer 5

Any nonempty string
Any number
An empty array
An empty object
An empty function

Question 6

Why might you want to use a bigint data type rather than a number data type?

Answer 6

bigint has a higher amount of precision for integers higher than 2*10^53

Question 7

What is the object data type?

Answer 7

A collection of key values pairs inside curly braces

Question 8

What is the symbol data type?

Answer 8

Represents a unique identifier that can be used within objects.

Question 9

What is the difference between assigning a variable with let versus const?

Answer 9

Variables assigned using const can’t be reassigned.

Question 10

What is the difference between prefixing and postfixing - - and ++?

Answer 10

Prefixing will return the value and then increment it. Postfixing will increment the value and then return it.

Question 11

How do you find out the type of a variable?

Answer 11

typeof(x) or just typeof x