"

From 2013.igem.org

/*!

* jQuery Scrollspy Plugin
* Author: @sxalexander
* Licensed under the MIT license
*/

(function ( $, window, document, undefined ) {

   $.fn.extend({
     scrollspy: function ( options ) {
       
         var defaults = {
           min: 0,
           max: 0,
           mode: 'vertical',
           buffer: 0,
           container: window,
           onEnter: options.onEnter ? options.onEnter : [],
           onLeave: options.onLeave ? options.onLeave : [],
           onTick: options.onTick ? options.onTick : []
         }
         
         var options = $.extend( {}, defaults, options );

         return this.each(function (i) {

             var element = this;
             var o = options;
             var $container = $(o.container);
             var mode = o.mode;
             var buffer = o.buffer;
             var enters = leaves = 0;
             var inside = false;
                           
             /* add listener to container */
             $container.bind('scroll', function(e){
                 var position = {top: $(this).scrollTop(), left: $(this).scrollLeft()};
                 var xy = (mode == 'vertical') ? position.top + buffer : position.left + buffer;
                 var max = o.max;
                 var min = o.min;
                 
                 /* fix max */
                 if($.isFunction(o.max)){
                   max = o.max();
                 }

                 /* fix max */
                 if($.isFunction(o.min)){
                   min = o.min();
                 }

                 if(max == 0){
                     max = (mode == 'vertical') ? $container.height() : $container.outerWidth() + $(element).outerWidth();
                 }
                 
                 /* if we have reached the minimum bound but are below the max ... */
                 if(xy >= min && xy <= max){
                   /* trigger enter event */
                   if(!inside){
                      inside = true;
                      enters++;
                      
                      /* fire enter event */
                      $(element).trigger('scrollEnter', {position: position})
                      if($.isFunction(o.onEnter)){
                        o.onEnter(element, position);
                      }
                     
                    }
                    
                    /* triger tick event */
                    $(element).trigger('scrollTick', {position: position, inside: inside, enters: enters, leaves: leaves})
                    if($.isFunction(o.onTick)){
                      o.onTick(element, position, inside, enters, leaves);
                    }
                 }else{
                   
                   if(inside){
                     inside = false;
                     leaves++;
                     /* trigger leave event */
                     $(element).trigger('scrollLeave', {position: position, leaves:leaves})

                     if($.isFunction(o.onLeave)){
                       o.onLeave(element, position);
                     }
                   }
                 }
             }); 

         });
     }

   })

})( jQuery, window );