NaN is a JavaScript property, which is "Not-a-Number" value. This shows it is not a legal number.
Syntax
Here’s the syntax −
Number.NaN
Example
To find out whether value is NaN, use the Number.isNaN() or isNan() method. Here’s an example to check −
Live Demo
<!DOCTYPE html>
<html>
<body>
<button onclick="display()">Check</button>
<p id="test"></p>
<script>
function display() {
var a = "";
a = a + isNaN(6234) + ": 6234<br>";
a = a + isNaN(-52.1) + ": -52.1<br>";
a = a + isNaN('Hello') + ": 'Hello'<br>";
a = a + isNaN(NaN) + ": NaN<br>";
a = a + isNaN('') + ": ''<br>";
a = a + isNaN(0) + ": 0<br>";
a = a + isNaN(false) + ": false<br>";
document.getElementById("test").innerHTML = a;
}
</script>
</body>
</html>