JavaScript Number NaN Property

In JavaScript, NaN stands for Not a Number. It represents a value that is not a valid number. It can be used to check whether a number entered is a valid number or not a number. To assign a variable to NaN value, we can use one of the two following ways.

Syntax:

let a = NaN
    // OR
let a = Number.NaN

Example 1: In this example, we will use JavaScript Number NaN Property.

javascript

let monthNumber = 14;

if (monthNumber < 1 || monthNumber > 12) {

    // Assigning monthNumber NaN as
    // month number is not valid
    monthNumber = Number.NaN;

    console.log("Month number should be"
                + " between 1 and 12");
}
else {
    console.log(monthNumber);
}

Output:

Month number should be between 1 and 12

Example 2: Whenever we try to parse a string or “undefined” to an int, it returns NaN. 

javascript

console.log(parseInt("higeeks"));

Output:

Nan

Example 3: Whenever we try to find square root of a negative number using Math.sqrt function, it returns NaN.

javascript

console.log(Math.sqrt(-1));

Output:

NaN

Example 4: Whenever we try to make on operation on NaN, it returns NaN.

javascript

console.log(5 + NaN);

Output:

NaN

Example 5: Any indeterminate form also returns NaN.

javascript

console.log(0 * Infinity)

Output:

NaN

Example 6: Any operation other than addition on a string also results in NaN.

javascript

console.log("hi"/5)

Output:

NaN

Supported Browser: 

• Chrome 1 and above
• Edge 12 and above
• Firefox 1 and above
• Internet Explorer 4 and above
• Opera 3 and above
• Safari 1 and above

We have a Cheat Sheet on Javascript Numbers where we covered all the important topics of Javascript to check those please go through JavaScript Number Complete Reference.