The isNaN() function is used to check whether a given value is an illegal number or not. It returns true if value is a NaN else returns false. It is different from the Number.isNaN() Method.

Syntax:

isNaN( value )

Parameter Values: This method accepts single parameter as mentioned above and described below:

• value: It is a required value passed in the isNaN() function.

Return Value: It returns a Boolean value i.e. returns true if the value is NaN else returns false.

Output:

false
true
false
true
true
false
true

Supported Browsers:

• Chrome
• Firefox
• Edge
• Opera
• Safari