[Javascript] Identify and Deal with NaN in JavaScript

Dealing with the special

NaN

value can be tricky in JavaScript. It behaves like a number and not a number at the same time. This lesson explains how to identify it using the

isNaN

function or the

Number.isNaN

method.

Number.isNaN = Number.isNaN  || function(x) {x !== x}

Number.isNaN(NaN) // true
Number.isNaN("JS") // false
Number.isNaN("") // false