Description

The JavaScript Number method isNaN() checks whether the given number is a NaN (nothing but Not-a-Number).

  • It returns true if the value is NaN and its type is a Number.
  • It is a static method, so it can be directly accessed using the class Number and doesn't need its instance.
  • NaN is considered a number but not a legal number.

Syntax

The method isNaN() has the below syntax, where num is a number.

Number.isNaN(num)

Parameters

The method isNaN() allows the below parameters.

num

  • It is a number to be checked for being a NaN.

Result

Returns true if the given number is a NaN with type Number, otherwise returns false.

Example 1: Using the Method

The below example shows the basic usage of the method.

// Returns true
console.log(Number.isNaN(0/0));         // Prints: true

// Returns false
console.log(Number.isNaN(123));             // Prints: false
console.log(Number.isNaN("123"));           // Prints: false
console.log(Number.isNaN(123.45));          // Prints: false
console.log(Number.isNaN("Hello"));         // Prints: false
console.log(Number.isNaN("2020/12/31"));    // Prints: false
console.log(Number.isNaN(Infinity));        // Prints: false
console.log(Number.isNaN(-Infinity));       // Prints: false

Output:

true
false
false
false
false
false
false
false

Overall

The JavaScript Number method isNaN() checks whether the given number is a NaN (nothing but Not-a-Number).

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