Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<body>

<iframe id="myFrame" src="../default.asp.html" height="200" width="250"></iframe>

<p>Click the button to display the height of the iframe.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.getElementById("myFrame").height;
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>