web/lib/visible.js

   1 (function($){
   2
   3         /**
   4          * Copyright 2012, Digital Fusion
   5          * Licensed under the MIT license.
   6          * http://teamdf.com/jquery-plugins/license/
   7          *
   8          * @author Sam Sehnert
   9          * @desc A small plugin that checks whether elements are within
  10          *               the user visible viewport of a web browser.
  11          *               only accounts for vertical position, not horizontal.
  12          */
  13         $.fn.visible = function(partial){
  14
  15             var $t                              = $(this),
  16                 $w                              = $(window),
  17                 viewTop                 = $w.scrollTop(),
  18                 viewBottom              = viewTop + $w.height(),
  19                 _top                    = $t.offset().top,
  20                 _bottom                 = _top + $t.height(),
  21                 compareTop              = partial === true ? _bottom : _top,
  22                 compareBottom   = partial === true ? _top : _bottom;
  23
  24                 return ((compareBottom <= viewBottom) && (compareTop >= viewTop));
  25     };
  26 })(jQuery);