JavaScript Oddities - Null and NaN

console.log(typeof null) //object
console.log(null instanceof Object) //false

We all know that value null represents intentional absence of any object value. typeof would return a string, hence typeof null returns object. This is a historical bug (since the first version of JavaScript) and cannot be fixed.

But since null is absence of value, it implies it cannot be instance of anything, hence instanceof returns a false value.

Similarly,

console.log(typeof NaN) //Number
console.log(NaN === NaN) //false

NaN is a number from data type point of view. NaN is a special number as specified by IEEE format specification and is not JavaScript language specific. NaN is never equal to NaN, as each NaN is unique unknown number.