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JavaScript Number NaN Property

The JavaScript Number NaN is a static property that represents a value that is Not-A-Number. Because it is a static property of the Number object, you can access it directly by using Number.NaN, instead of as a property of a variable.

If you try to access this property using a variable as x.NaN, where 'x' is a variable, you will get 'undefined' as the result. This is because NaN is a static property of the Number object, not a property of individual variables.

Syntax

Following is the syntax of JavaScript Number NaN property −

Number.NaN

Parameters

  • It does not accept any parameter.

Return value

This property does not have any return value.

Example 1

The following program demonstrates the use of the Number.NaN property.

<html>
<head>
<title>JavaScript Number NaN Property</title>
</head>
<body>
<script>
   document.write("Result = ", Number.NaN);
</script>
</body>
</html>

Output

The above program returns 'NaN' in the output.

Result = NaN

Example 2

If you try to access this property using a variable rather than the Number object, you will get 'undefined' as the result.

<html>
<head>
<title>JavaScript Number NaN Property</title>
</head>
<body>
<script>
   let x = 10;
   document.write("x = ", x);
   document.write("<br>x.NaN is = ", x.NaN);
</script>
</body>
</html>

Output

The above program displays 'undefined' because the variable cannot access the 'NaN' property.

x = 10
x.NaN is = undefined

Example 3

The following program checks a number and returns Number.NaN if it is not a valid number; otherwise, it displays "passed".

<html>
<head>
<title>JavaScript Number NaN Property</title>
</head>
<body>
<script>
   function check(x){
      if(isNaN(x)){
         return Number.NaN;
      }
      else{
         return x + " is a number...!";
      }
   }
   let x = 10;
   document.write("x = ", x);
   document.write("<br>Result1 = ", check(x));
   let y = NaN;
   document.write("<br>y = ", y);
   document.write("<br>Result2 = ", check(y));
</script>
</body>
</html>

Output

The above program displays the output based on conditions (for true, Number.NaN; and for false, a statement will be returned).

x = 10
Result1 = 10 is a number...!
y = NaN
Result2 = NaN
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