How can I run if condition inside this function

Question

var myDiv = document.getElementById("div"),
    myInput = document.getElementById("input"),
    theAges = document.getElementById("ages");

//Element.event = function () {// code}

theAges.onchange = function() {
  "use strict";

  myDiv.innerHTML = myInput.value * theAges.value;

  if (myInput.value === isNaN()) {
    myDiv.innerHTML = "this is not a number";
  }
};

Answer 1

Try this :

if (isNaN(myInput.value))

isNaN is a function that take in parameter the value you want to test and return a boolean.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/isNaN