Javascript: Check an image is Loaded or Not

How can we check whether an image is loaded fully or
partially using javascript. It is possible
See the Example Below.

function IsImageOk(img) {
// During the onload event, IE correctly identifies
any images that
// weren’t downloaded as not complete. Others should too. Gecko-based
// browsers act like NS4 in that they report this incorrectly.
if (!img.complete) {
return false;
}

// However, they do have two very useful properties:
naturalWidth and
// naturalHeight. These give the true size of the image. If it failed
// to load, either of these should be zero.
if (typeof img.naturalWidth
!= “undefined” && img.naturalWidth
== 0) {
return false;
}

// No other way of checking: assume it’s ok.
return true;
}

//Call this function onLoad of body tag
function checkImages() {
for (var i = 0; i < document.images.length; i++) {
if (!IsImageOk(document.images[i])) {

document.images[i].src = “/images/loaderror.jpg“;
}
}
}