jquery.scrollzip.js

/**
* jQuery scrollzip Plugin 1.0
*
* http://www.tinywall.net/
*
* Copyright (c) 2013 Arun David
*/
(function($){
    $(window).on("load",function(){
        $(document).scrollzipInit();
    });
    $.fn.scrollzipInit=function(){
        $('body').prepend("<div style='position:fixed;top:0px;left:0px;width:0;height:0;' id='scrollzipPoint'></div>" );
    };
    $.fn.scrollzip = function(options){
        var settings = $.extend({
            showFunction    : null,
            hideFunction    : null,
            showShift       : 0,
            wholeVisible    : false,
            hideShift       : 0,
        }, options);
        return this.each(function(i,obj){
            $(this).addClass('scrollzip');
            if ( $.isFunction( settings.showFunction ) ){
                if(
                    !$(this).hasClass('isShown')&&
                    ($(window).outerHeight()+$('#scrollzipPoint').offset().top-settings.showShift)>($(this).offset().top+((settings.wholeVisible)?$(this).outerHeight():0))&&
                    ($('#scrollzipPoint').offset().top+((settings.wholeVisible)?$(this).outerHeight():0))<($(this).outerHeight()+$(this).offset().top-settings.showShift)
                ){
                    $(this).addClass('isShown');
                    settings.showFunction.call( this );
                }
            }
            if ( $.isFunction( settings.hideFunction ) ){
                if(
                    $(this).hasClass('isShown')&&
                    (($(window).outerHeight()+$('#scrollzipPoint').offset().top-settings.hideShift)<($(this).offset().top+((settings.wholeVisible)?$(this).outerHeight():0))||
                    ($('#scrollzipPoint').offset().top+((settings.wholeVisible)?$(this).outerHeight():0))>($(this).outerHeight()+$(this).offset().top-settings.hideShift))
                ){
                    $(this).removeClass('isShown');
                    settings.hideFunction.call( this );
                }
            }
            return this;
        });
    };
})(jQuery);