How to use isnan in js

isNaN() function is used to check whether a value is a non-numeric value (NaN). Usage: Pass the value to check as parameter, return true if it is NaN, otherwise return false. Note: isNaN() also returns true for strings, booleans, and null values. Use the Number.isFinite() function to check for a finite number. Use isNaN(value) !== true to check for undefined values.

isNaN() in JavaScript

What is isNaN()?

isNaN() is a built-in function in JavaScript that checks whether a value is a non-numeric value, that is, NaN (Not a Number).

Syntax

isNaN(value)

where value is the value to be checked.

How to use

To use isNaN(), simply pass the value you want to check as a parameter to the function.

Return value

isNaN() Returns a Boolean value:

• ifvalue is a non-numeric value (NaN), then true is returned.
• If value is a numeric value, false is returned.

Notes

The following are some things to note when using isNaN():

• isNaN() Also returns true for strings, booleans, and null values.
• To check whether the value is a finite number, you can use the Number.isFinite() function.
• To use isNaN() to check for an undefined value, use isNaN(value) !== true.

Example

console.log(isNaN(NaN)); // true
console.log(isNaN(1)); // false
console.log(isNaN('abc')); // true
console.log(isNaN(true)); // true
console.log(isNaN(null)); // true

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