Tryit Editor v2.9

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

<img id="myImg" src="compman.gif" style="width:250px;height:300px;">

<p>Click the button to return the width of the image.</p>

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

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

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

</body>
</html>