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Javascript > Javascript > Flashcards

Javascript Flashcards

1
Q

Code for

Exponent or Power

A

(**) or Math.pow(baseNumber, powerNumber)
Example: 2 ** 5 = 32

For squared exponent or power will always be 2
(6 ** 2), (20 ** 2), (3 ** 2)

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2
Q

Find remainder

A

(%)
example: 11 % 2 = 1

finds the remainder
(Since 2 goes into 11, 5 times, the remainder is 1)
If using % 2 and remainder is 1, number is odd. If remainder is 0, number is even

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3
Q

Sum (Plus-equals) (Increment)

Minus-equals (Decrement)

Product (Times-equals) (Multiplier)

Divide-equals (Divider)

A

Sum (+=)
Example: 11 += 2 = 13

Decrement (-=)
Example: 11 -= 2 = 9

Product (*=)
Example: 11 *= 2 = 22

Divider (/=)
Example: 12 /= 2 = 6

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4
Q

Find Absolute Value

A

Math.abs()

Example: Math.abs(-295) = 295

Measures distance from 0
Answer will always be positive

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5
Q

Round Up

A

Math.ceil()

Example: Math.ceil(33.7) = 34

Rounds up

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6
Q

Round Down

A

Math.floor()

Example: Math.floor(33.7) = 33

Rounds down

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7
Q

Code for

Parsing an integer from a string

A

Number.parseInt()

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8
Q

Code for

Parsing a float from a string

A

Number.parseFloat()

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9
Q

Generate a random Number

A

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

Example: Math.random() * (10 - 1) + 1 =
Random number between 10 and 1

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10
Q

Boolean Operator for

Not

A

(!)

Example: (!true = false), (!boolean = notBoolean)

Creates Opposite

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11
Q

Boolean Operator for

Or

A

(||)

Example: (true || true = true), (true || false = true)
(false || false = false)

Both variables must be false to return false
All else is true

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12
Q

Boolean Operator for

And

A

(&&)

Example: (false && false = false), (true && false = false)
(true && true = true)

Both variables must be true to return true
All else is false

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13
Q

Boolean Operator for

Equal to

A

(===)

Example: (true === true = true), (false === false = true)
(true === false = false)

Both variables must be the same to return true
All else is false

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14
Q

Boolean Operator for

Not equal to

A

(!==)

Example: (true !== false = true), (false !== true = true)
(true !== true = false)

Both variables must be different to return true
All else is false

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15
Q

Find a Character in a string

A

“string”[index]

Example: “computer”[3] = p

Gets a specific character in a string
index always starts at 0

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16
Q

Add together two or more strings without a space

Add together two or more strings with a space

A

(without a space)
“string1” + “string2”

Example: “comp” + “uter” = computer

(with a space)
“string1” + “ “ + “string2”

Example: “John” + “ “ + “Smith” = John Smith

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17
Q

Interpolate a string

A

+ parameters +

Example:
“We will go “ + hiking + “ on “ + Tuesday + “.”
=
we will go hiking on Tuesday

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18
Q

Get the length of a string

A

“string”.length

Example: “Apple”
“string”.length = 5

Tells you the length of the string

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19
Q

Get the last character of a string

A

“string”[“string”.length - 1]

Example: “banana”
“string”[“string”.length - 1] = a

Tells you the last character in the string

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20
Q

Get a portion of a string

A

“string”.substring(parameters)

Example: “Queue”
“string”.substring(1, 4) = ueu

Tells you a specific portion of a string
Starts at 0, ends before 2nd parameter

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21
Q

Find the beginning index of a portion of a string

A

“string”.indexOf(substring)

Example: “Quicksort”
“string”.indexOf(“sort”) = 5

Tells you the index where a substring starts
Starts at 0

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22
Q

Change not a string into a string

A

parameter.toString()
(fill in parameter), (leave () blank)

Example: 54.toString = “54”

converts parameter into single string

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23
Q

Accessing an element in an Array

A

Array[index]

Example:
[water, coffee, tea][2]
array[index] = tea

Tells you the element at the given index
Index starts at 0

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24
Q

Get the length of an Array

A

Array.length

Example:
[1, 3, 4, 5, 7]
array.length = 5

Tells you the number of elements in an array

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25
Q

Remove the last element of an array

A

array.pop()
(leave () blank)

Example: 
[1, 2, 3]
array.pop() ;
return array ;
= [1, 2]

Tells you the last element in an array

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26
Q

Add an element to the front of an array

A

array.unshift(newElement)

Example: 
[1, 2]
array.unshift(3) ;
return array ;
= [3, 1, 2]

Adds new element to front of array

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27
Q

Add an element to the back of an array

A

array.push(newElement)

Example: 
[1, 2]
array.push(3) ;
return array ;
= [1, 2, 3]

Adds new element to back of array

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28
Q

Remove an element from an array

A

array.splice(index where to delete, how many to delete)

Example:
[8, 9, 10, 10000, 11]
array.splice(3, 1) = [8, 9, 10, 11]

Removes indicated element
Index starts at 0

29
Q

Add/remove an element to an array

A

array.splice
(index add/delete, how many delete, newElements)

Example: Add
[8, 9, 10, 12].splice(3, 0, 11) = [8, 9, 10, 11, 12]

Example: add and delete
[8, 9, 10, 24, 17, 13]
array.splice(3, 2, 11, 12) = [8, 9, 10, 11, 12, 13]

Adds or Adds/Removes elements in an array
Index starts at 0

30
Q

Determine if value is an array

A

Array.isArray(input)

Example: Array.isArray([1, 2, 3]) = true

Tells you whether or not the input is an array

31
Q

Copy an array or part of an array

A

array.slice(start index, end index)

Example: copy part of an array
[‘q’, ‘u’, ‘e’, ‘u’, ‘e’].slice(1, 4) = [‘u’, ‘e’, ‘u’]

Example: copy entire array
[‘q’, ‘u’, ‘e’, ‘u’, ‘e’]
array.slice() = [‘q’, ‘u’, ‘e’, ‘u’, ‘e’]

Leave () blank to copy entire array

32
Q

Add one array to another array

A

result.concat(array)

Example:
var result = []
array of arrays[ ['a', 'b'], ['c', 'd'], ['e', 'f'] ]
result = result.concat(array[i]) 
return result
= ['a', 'b', 'c', 'd', 'e', 'f']

Combines multiple arrays

33
Q

Turn an array into a string

A

array.join(element to replace comma in array)

Example: [“my”, “name”, “is”]
array.join(“ “) = my name is

Turns an array into a string

34
Q

Turn a string into an array

A

string.split(element to replace with a comma)

Example:
var name: “my name is”
name.split(“ “) = [“my”, “name”, “is”]

Turns a string into an array

35
Q

Find the index of an element of an array

A

array.indexOf(element)

Example: [“this”, “is”, “crazy”]
array.indexOf(“is”) = 1

Tells you the index of the element
Index starts at 0

36
Q

Access a value in an object

A

object[key]

Example: 
{who: "me", when: "now", what: "tea"}
["when"]
obj[key] = "now"
Tells you the property at the key in the object
37
Q

Remove a property (key: value) from an object

A

delete object[key]

Example:
{who: "me", when: "now", what: "tea"}
["when"]
delete obj[key]
= {who: "me", what: "tea"}

Deletes both key and “property” at given key in object

38
Q

Average

A

Sum of numbers divided by amount of numbers

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

39
Q

Area of a Triangle

A

(Base x Height) / 2

40
Q

Number Cubed

A

Any number to the power of 3

Example: 3 ** 3 = 27

41
Q

Number Squared

A

Any number to the power of 2

Example: 3 ** 2 = 9

42
Q

Area of a Rectangle

A

Length * Width

43
Q

Perimeter of a Circle

A

2 * Math.PI * radius

Math.PI is code for Pi

44
Q

Code for Pi

A

Math.PI

45
Q

Area of a Circle

A

Math.PI * radius ** 2

Pi times the Radius to the Power of 2 (or squared)

46
Q

Square Root

A

Math.sqrt(number)

47
Q

Remove from front of an array

A

array.shift()
(leave () blank)

Example:
 [1, 2, 3]
array.shift() ;
    return array ;
= [2, 3]
48
Q

Strings have length properties.

Numbers do not have length properties.

Arrays do have a length property.

A 
var string = "hello"
string.length = 5
var number = 1
number.length = undefined
49
Q

.length includes spaces when measuring a string

A 
var string = "what is up"
string.length = 10
50
Q

What is an object

A

An object is a datatype that helps us collect and organize many pieces of data.
Inside is going to be
Key: Value
(Property)

51
Q

What is an Array

A

A piece of data that organizes many pieces of data.
Can be anything from strings, to booleans, to numbers. Or even more nested arrays in an array. You can also have an object in an array.

52
Q

What is an Array

A

One piece of data that organizes many pieces of data.
Can be anything from strings, to booleans, to numbers. Or even more nested arrays in an array. You can also have an object in an array.

53
Q

Property

A

key: value

A property can only have one key and one value

54
Q

Keys are strings

A

{
madeByAWizard: true
}
madeByAWizard is a string

55
Q 
Dot Notation
(shortcut)
A 
Dot Notation will find the named key and output the value at named key. 
shortcut to bracket notation
var magicObj =
{
secretCode: "open sesame"
}
magicObj.secretCode
returns      open sesame
56
Q

Bracket Notation

best to use

A 
You can use bracket notation for any situation trying to get a value from an obj.
var magicObj =
{
secretCode: "open sesame"
}
magicObj["secretCode"]
returns        open sesame

If putting a variable in Brackets you do not need “”

57
Q

Using a variable to represent a key

Bracket Notation

A 
var magicObj = 
{
familiars: ["frog", "bat", "cat", "owl"]
}
var animals = "familiars"
magicObj[animals]
returns
["frog", "bat", "cat", "owl"]
58
Q

console.log

A

kind of works as notes. You cant actually use it.

Maybe your in your code and are wondering if the var howMuch is equal to 11, you can console.log.

var howMuch = 11
console.log(11 === howMuch)

it will return true of false

console.log outside of function

59
Q

Return

A

Returns the result or something that can be used in your code

return is always the last thing that your function does. Nothing else can happen after that

60
Q

Function

A

A set of instructions that we want the computer to execute

61
Q

typeof cannot tell the difference between an array and an object.
How do you figure out if something is an array?

A

Which is why we must use Array.isArray to figue out if it is an array.

62
Q

Convert an Object into an Array

A

…

63
Q

Convert an Array into an Object

A

…

64
Q

You know something is a function because it has parenthesis ()

A

array. pop()

array. unshift()

65
Q

Type of

A

if (typeof(input) === “number”)

if (typeof(input) === “string”)

66
Q

Sumnation

A

Sumnation of the number 6
add all number below 6
1+2+3+4+5+6 = 21

How to: n = 6
var sumnation = 0
-- iterate over the single number
-- there is no length
for (var i = 0; i <= n; i++)
-- i needs to be <= to n because i is what we are adding
-- add i to sumnation
sumnation += i
return sumnation;
= 21
67
Q

factorial

A

Factorial of the number 4
multiply all the numbers below 4
432*1 = 24
var must be 1 because of multiplication

How to: n = 4
var factorial = 1
-- iterate over single number
for (var i = 1; i <= n; i++)
-- i must be <= n
-- multiply i by factorial
factorial *= i
return factorial;
= 24
68
Q

Compound Interest

A 
// I = P(1 + (r/n)) ^ (n*t) - P
  // n is compoundingFrequency
  // t is timeInYears
  // r is interestRate
Example:
var compoundedInterest = (principal * Math.pow(1 + (interestRate/compoundingFrequency) , (compoundingFrequency * timeInYears))) - principal
return compoundedInterest; }
69
Q

Multiply between/ Sum between

starts at first number

A

(num1, num2) (2, 5)

var product = 1
for (var i = num1; i < num2; i++)
product = product * i
return product;
= 24

//starts at first number

Javascript (2 decks)

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