Javascript quick study

Question 1

remove from front

Answer 1

array.shift()

leave () blank

Question 2

remove from back

Answer 2

array.pop()

leave () blank

Question 3

add to front

Answer 3

array.unshift(new element)

Question 4

add to back

Answer 4

array.push(new element)

Question 5

absolute value

Answer 5

Math.abs(number)
//always positive

Question 6

round up

Answer 6

Math.ceil(number)

Question 7

round down

Answer 7

Math.floor(number)

Question 8

Generate random number

Answer 8

Math.random() * (max - min) + min)

leave () blank

Question 9

Not

Answer 9

!

Question 10

Or

Answer 10

||

Question 11

And

Answer 11

&&

Question 12

Equal to

Answer 12

===

Question 13

Not equal to

Answer 13

!==

Question 14

Get character in a string

Answer 14

“string”[index]

Question 15

Get length

Answer 15

.length

Question 16

Get an element in an array

Answer 16

array[index]

Question 17

Is it an array

Answer 17

Array.isArray(input)

Question 18

Add arrays together

Answer 18

array1.concat(array2, array3)

Question 19

Turn a string into an array

Answer 19

“string”.split(“ “)

var name: “my name is”
name.split(“ “) = [“my”, “name”, “is”]
(“ “) means split at the space

Question 20

Copy an Array

Answer 20

array.slice()

Question 21

Access a value in an object

Answer 21

object[key]

Question 22

Remove a property (key: value) from an object

Answer 22

delete object[key]

Question 23

Average

Answer 23

Sum of numbers divided by amount of numbers

Example: 12 + 27 + 5 + 9 = 53. 53/5 = 10.6

Question 24

Area of a Triangle

Answer 24

(Base x Height) / 2

Question 25

Area of a Rectangle

Answer 25

Length * Width

Question 26

Perimeter of a Circle

Answer 26

2 * Math.PI * radius

Question 27

Code for PI

Answer 27

Math.PI

Question 28

Area of a Circle

Answer 28

Math.PI * radius ** 2

Question 29

Square Root

Answer 29

Math.sqrt(number)