JavaScript NaN

In JavaScript, NaN is short for Not a Number.

NaN is a JavaScript number that is not a legal number.

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Invalid Number Operations

You get NaN when JavaScript cannot calculate a number.

Example

let x = 100 / "Apple";

document.getElementById("demo").innerHTML = x;

NaN is a Number

The type of NaN is number.

This may look strange, but NaN belongs to the JavaScript number type.

Example

let x = NaN;

document.getElementById("demo").innerHTML = typeof x;

Numeric Strings

JavaScript tries to convert numeric strings to numbers in arithmetic operations.

Example

let x = 100 / "10";

document.getElementById("demo").innerHTML = x;

Non-Numeric Strings

A non-numeric string cannot be converted to a number.

Example

let x = 100 / "Apple";

document.getElementById("demo").innerHTML = x;

Using isNaN()

You can use the JavaScript function isNaN() to find out if a value is not a number.

Example

let x = 100 / "Apple";

document.getElementById("demo").innerHTML = isNaN(x);

NaN is Not Equal to Itself

NaN is the only JavaScript value that is not equal to itself.

Example

let x = NaN;

document.getElementById("demo").innerHTML = x == x;

To test for NaN, use isNaN().

NaN in Math

If you use NaN in a mathematical operation, the result will also be NaN.

Example

let x = NaN;

let y = 5;

document.getElementById("demo").innerHTML = x + y;