?;$(function()
?? {
?????? 'use strict';

?????? var sidebar = $('#sidebar'),
??????? mask = $('.mask'),
??????? backButton = $('.back-to-top'),
??????? sidebar_trigger = $('#sidebar_trigger');

?????? function showSideBar()
????? {
??????? mask.fadeIn();
??????? sidebar.css( 'right', 0 );
?????? }
????? function? hideSideBar()
????? {
??????? mask.fadeOut();
??????? sidebar.css('right', -sidebar.width());
????? }
?????? sidebar_trigger.on('click', showSideBar);
??????? mask.on('click', hideSideBar);
??????? backButton.on('click',function()
?????? {
?????????? $('html,body').animate({
?????????????? scrollTop: 0
?????????? },800);
??????? })
????? $(window).on ('scroll',function()
?????? {
?????????? if($(window).scrollTop() > $(window).height())
?????????? {
?????????????? backButton.fadeIn();
?????????? }
?????????? else {
?????????????? backButton.fadeOut();
?????????? }
?????? })
?????? $(window).trigger('scroll');
?})