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<!DOCTYPE html>
<html>
<body>
<h2>JavaScript Comparisons</h2>
<p>Input your age and click the button:</p>
<input id="age" value="18" />
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
  let voteable;
  let age = Number(document.getElementById("age").value);
  if (isNaN(age)) {
    voteable = "Input is not a number";
  } else {
    voteable = (age < 18) ? "Too young" : "Old enough";
  }
  document.getElementById("demo").innerHTML = voteable + " to vote";
}
</script>
</body>
</html>