getting size of the image using javascript

--------------------------------------------------------
<script language="JavaScript">
function getImgSize(imgSrc)
{
var newImg = new Image();
newImg.src = imgSrc;
var height = newImg.height;
var width = newImg.width;
alert ('The image size is '+width+'*'+height);
}
</script>

<img src="images/plus_icon.png" id="demoImg" />
<button onclick="getImgSize(document.getElementById('demoImg').src);" value="Click Me">click me</button>



--------------------------------------------------------