How do you check that a number is NaN in JavaScript?

JavascriptWeb DevelopmentFront End Technology

NaN is a JavaScript property, which is Not-a-Number value. This shows it is not a legal number. Here’s the syntax −

Syntax

Number.NaN

To find out whether a number is NaN, use the Number.isNaN() or isNan() method. Here’s an example to check −

Example

Live Demo

<!DOCTYPE html>
<html>
   <body>
      <button onclick="display()">Check</button>
      <p id="test"></p>
      <script>
         function display() {
            var a = "";
            a = a + isNaN(434) + ": 434<br>";
            a = a + isNaN(-23.1) + ": -23.1<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>
raja
Published on 03-Feb-2018 17:05:48
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