What is NaN?

NaN is a special value that represents "Not a Number". It is used to indicate that a value is not a valid number, usually as the result of an invalid mathematical operation.

NaN is a type of value known as a "primitive value", along with other values such as null, undefined, and boolean values (true and false).

You can check if the value of a variable is NaN using the isNaN() function, which is a global function in JavaScript that returns true if the value is NaN and false if it is a valid number.

const NAN = NaN;
const alsoNan = 'string' / 10;

NAN === alsoNan; // false
isNaN(NAN); // true
isNaN(alsoNan); // true