Global-Methods

Question 1

isFinite

Answer 1

isFinite({mixed} value)
=>  {bool} whether the value is finite
#global
#safe
#alternative
- better to use ES6 Number.isFinite, since it won't try and convert the value into a number

value

• can be any data type (since global), isFinite will convert value to number or NaN
• NaN, Infinity, -Infinity produce false

Question 2

isNaN

Answer 2

isNaN({mixed} value)
=>  {bool} whether the value is NaN
#global
#safe
#dontuse
- either use `value !== value` or ES6 alternative Number.isNan()

Question 3

parseInt

Answer 3

parseInt({str} value, -{num=10} base)
=>  {num} integer representation of value at base of `base`, else NaN if number can't be produced
#global
#safe BUT base default defined by ES5

value

• string representation, else, converted into string first
• decimal digits are truncated (NOT rounded)
• parseInt() will return prematurely when value contains character not recognized by base notation, unless the character is the first character, in which case, NaN is returned

Question 4

parseFloat

Answer 4

parseFloat({str} value)
=>  {num} decimal number representation of value
#global
#safe

value

• string representation, else, converted into string first
• parseFloat() will return prematurely when value contains characters NOT [0-9.-+e], unless the character is the first character, in which case, NaN is returned.