NaN in JavaScript

NaN represents “Not-a-Number” value. It indicates a value which is not a legal number.

  • typeof of a NaN will return a Number.

isNaN() function

To check if a value is NaN, we use the isNaN() function.

isNaN("Hello") // Returns true
isNaN(345) // Returns false
isNaN('1') // Returns false, since '1' is converted to Number type which results in 0 ( a number)
isNaN(true) // Returns false, since true converted to Number type results in 1 ( a number)
isNaN(false) // Returns false
isNaN(undefined) // Returns true

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