Created at 773 days ago

isNaN() vs Number.isNaN()

There are two isNaN() functions:

• isNaN() determines whether a value is NaN, first converting the value to a number if necessary.
• Number.isNaN() determines whether the passed value is the number value NaN.

isNaN() can use to test whether an value to is arithmetically processable (usable "like" a number). And Number.isNaN() doesn't attempt to convert the parameter to a number, so non-numbers always return false.

isNaN(NaN) //true
Number.isNaN(NaN) // true

isNaN(123) // false
Number.isNaN(123) // false

isNaN('123') // false
Number.isNaN('123') // false

isNaN('abc') // true
Number.isNaN('abc') // false