// The client side event PrevButtonClicked takes two parameters, sender and e.
// Sender is the object which is raising the event
// e is the ImageViewerButtonEventArgs
function WebImageViewer_PrevButtonClicked(sender, e) {
var imageViewer = $find("WebImageViewer1");
// Get the HTML DOM element associated with the event
var buttonElement = e.getButtonElem();
// Get the scroll animation object
var scrollAnimations = imageViewer.get_scrollAnimations();
// Set the Animation type to continuous
scrollAnimations.set_type($IG.ScrollAnimation.Continuous);
// Specify the direction
imageViewer.navigatePrev();
}