IES: JS-deck 13

Question 1

JS isNaN ( )

Answer 1

• “Not a Number”
• JS built-in function
• Similar to parseFloat() and parseInt(), isNaN() first attempts to find a number at the beginning of the specified value
• Boolean: This function returns true if it cannot find a number at the beginning, and returns false if it does.
  Ex.
  ~~~
  let sum, net = ‘25’, tax = 5.00
  isNaN(net) ```
  (before the ‘$’ prefix is added),
  return = “false”
  isNaN(net)
  (after the ‘$’ prefix is added),
  return = “true”

Question 2

JS Coercion

Answer 2

• Conversion of data types
• can be explicit or implicit
• Implicit coercion:
  Ex. '42' + 8 = 428
• Explicit coercion:
  Ex. String(42)
  return = ‘42’

Question 3

JS String ()

Answer 3

• method
• Can return a string representation, in the string data type, of a number specified within its parantheses
  Ex. String (42)
  return = the number ‘42’ as a string data type

Question 4

JS toString()

Answer 4

• method
• you can append a call onto a variable name to return a string representation of a stored data type.
  Ex.
  (variable named “num” is assigned a number)
  num.toString()
  return = (a string version of that stored / assigned number)

Question 5

JS Operator “ + “

Answer 5

• Operation
  1. Addition of numbers
  2. Concatenation of strings

Question 6

JS Operator “ - “

Answer 6

• Operation: Subtraction

Question 7

JS Operator “ / “

Answer 7

• Operation: Division

Question 8

JS Operator “ % “

Answer 8

• Operation: Modulus
• returns the remainder of a division operation
• Divides the first operand by the second operand and returns the remainder

Question 9

JS Operator “ ++ “

Answer 9

• Operation: Increment
• Increases the operand value by 1 and returns the new value
• most commonly used to count iterations of a loop
• used in two different ways to subtly different effects
  1. when prefixing the operand, value is immediately changed before the expression is evaluated
  2. when post-fixing the operand, the expression is evaluated first then the value gets changed

Question 10

JS Operator “ – “

Answer 10

• Operation: Decrement
• Decreases the operand value by 1 and returns the new value
• most commonly used to count iterations of a loop
• used in two different ways to subtly different effects
  1. when prefixing the operand, value is immediately changed before the expression is evaluated
  2. when post-fixing the operand, the expression is evaluated first then the value gets changed

Question 11

JS Operator “ ** “

Answer 11

• Operation: Exponentiation
• Operator returns the result of a first operand raised to the power of a second operand

Question 12

JS Using modulus operator to determine a number’s parity

Answer 12

• Ex.

let parity = (numOne % 2 !==0) ? 'Odd' : 'Even'
console.log(numOne + 'is' + parity) 
 
parity = (numTwo % 2 !==0) ? 'Odd' : 'Even'
console.log(numTwo + 'is' + parity)

• HERE’S HOW IT WORKS:
  1. number % 2: This calculates the remainder when number is divided by 2.
  2. ?: This is the ternary operator. It checks if the result of number % 2 is truthy or falsy.
  3. If the remainder is 1 (or any non-zero value, which is truthy), it means the number is odd, and the expression after the ? is returned, which is ‘Odd’.
  4. If the remainder is 0 (which is falsy), it means the number is even, and the expression after the : is returned, which is ‘Even’.

Question 13

JS Operator “ ! “

Answer 13

• Logical NOT :
• This operator converts the operand to a boolean value and then inverts it.
• If the operand is truthy (a value that evaluates to true in a boolean context), ! makes it false. If it’s falsy (evaluates to false), ! makes it true.

Question 14

JS Operator “ == “

Answer 14

• The loose equality operator
  Ex.
  ==0
  checks if the value is loosely equal to zero

Question 15

JS “Operands”

Answer 15

• Values specified in Operation Statements
  Ex.
  5+2
  “5” & “2” are the operands

Question 16

JS Operator “ = “

Answer 16

• assignment operator
• Operators inclusive of “=” our shorthand forms of longer expression (excepting the simple “=” assignment operator)
• MEANS “assign,” NOT “equals” (to avoid confusion with the JS “===” equality operator)
• Example a=b
• Equivalent a=b (a gets assigned the value contained in variable b : becomes a’s new stored value)

Question 17

JS Operator “ += “

Answer 17

• Performs the arithmetical operation on the two operands first
• Then assigns the results of that operation to the first variable - so that becomes its new stored value.
• Example: a+=b
• Equivalent: a=(a+b)

Question 18

JS Operator “ -= “

Answer 18

• Performs the arithmetical operation on the two operands first
• Then assigns the results of that operation to the first variable - so that becomes its new stored value.
• Example: a-=b
• Equivalent: a=(a-b)

Question 19

JS Operator “ *= “

Answer 19

• Performs the arithmetical operation on the two operands first
• Then assigns the results of that operation to the first variable - so that becomes its new stored value.
• Example: a*=b
• Equivalent: a=(a*b)

Question 20

JS Operator “ /= “

Answer 20

• Performs the arithmetical operation on the two operands first
• Then assigns the results of that operation to the first variable - so that becomes its new stored value.
• Example: a/=b
• Equivalent: a=(a/b)