new file mode 100644

@@ -0,0 +1,24 @@

+function isOnScreen(elem) {

+    // if the element doesn't exist, abort

+    if (elem.length == 0) {

+        return;

+    }

+    var $window = jQuery(window);

+    var viewport_top = $window.scrollTop();

+    var viewport_height = $window.height();

+    var viewport_bottom = viewport_top + viewport_height;

+    var $elem = jQuery(elem);

+    var top = $elem.offset().top;

+    var height = $elem.height();

+    var bottom = top + height;

+

+    return (

+        (top >= viewport_top && top < viewport_bottom) ||

+        (bottom > viewport_top && bottom <= viewport_bottom) ||

+        (height > viewport_height &&

+            top <= viewport_top &&

+            bottom >= viewport_bottom)

+    );

+}

+

+