isNaN

The isNaN function checks if a value is NaN (Not-a-Number).

Syntax

isNaN(value)

Parameters

Name	Type	Description
value	any	Value to be checked.

Return Value

Type	Description
boolean	true if the value is NaN, else false.

Examples

isNaN(NaN);      // true
isNaN(10);       // false
isNaN('text');   // false

Notes

• Useful for mathematical validations and error control.
• This function strictly checks if the value is NaN, not if it can be converted to NaN.

References

• MDN: Number.isNaN()