https://kan-kyoten-musashino.jp/js/scrolltopcontrol.js

1//** jQuery Scroll to Top Control script- (c) Dynamic Drive DHTML code library: http://www.dynamicdrive.com.
2//** Available/ usage terms at http://www.dynamicdrive.com (March 30th, 09')
3//** v1.1 (April 7th, 09'):
4//** 1) Adds ability to scroll to an absolute position (from top of page) or specific element on the page instead.
5//** 2) Fixes scroll animation not working in Opera. 
6
7
8var scrolltotop={
9    //startline: Integer. Number of pixels from top of doc scrollbar is scrolled before showing control
10    //scrollto: Keyword (Integer, or "Scroll_to_Element_ID"). How far to scroll document up when control is clicked on (0=top).
11    setting: {startline:100, scrollto: 0, scrollduration:1000, fadeduration:[500, 100]},
12    controlHTML: '<div class="btn-pagetop"></div>',
13
14    controlattrs: {offsetx:20, offsety:160}, //offset of control relative to right/ bottom of window corner
15    anchorkeyword: '#top', //Enter href value of HTML anchors on the page that should also act as "Scroll Up" links
16
17    state: {isvisible:false, shouldvisible:false},
18
19    scrollup:function(){
20        if (!this.cssfixedsupport) //if control is positioned using JavaScript
21            this.$control.css({opacity:0}) //hide control immediately after clicking it
22        var dest=isNaN(this.setting.scrollto)? this.setting.scrollto : parseInt(this.setting.scrollto)
23        if (typeof dest=="string" && jQuery('#'+dest).length==1) //check element set by string exists
24            dest=jQuery('#'+dest).offset().top
25        else
26            dest=0
27        this.$body.animate({scrollTop: dest}, this.setting.scrollduration);
28    },
29
30    keepfixed:function(){
31        var $window=jQuery(window)
32        var controlx=$window.scrollLeft() + $window.width() - this.$control.width() - this.controlattrs.offsetx
33        var controly=$window.scrollTop() + $window.height() - this.$control.height() - this.controlattrs.offsety
34        this.$control.css({left:controlx+'px', top:controly+'px'})
35    },
36
37    togglecontrol:function(){
38        var scrolltop=jQuery(window).scrollTop()
39        if (!this.cssfixedsupport)
40            this.keepfixed()
41        this.state.shouldvisible=(scrolltop>=this.setting.startline)? true : false
42        if (this.state.shouldvisible && !this.state.isvisible){
43            this.$control.stop().animate({opacity:1}, this.setting.fadeduration[0])
44            this.state.isvisible=true
45        }
46        else if (this.state.shouldvisible==false && this.state.isvisible){
47            this.$control.stop().animate({opacity:0}

47, this.setting.fadeduration[1])
48            this.state.isvisible=false
49        }
50    },
51    
52    init:function(){
53        jQuery(document).ready(function($){
54            var mainobj=scrolltotop
55            var iebrws=document.all
56            mainobj.cssfixedsupport=!iebrws || iebrws && document.compatMode=="CSS1Compat" && window.XMLHttpRequest //not IE or IE7+ browsers in standards mode
57            mainobj.$body=(window.opera)? (document.compatMode=="CSS1Compat"? $('html') : $('body')) : $('html,body')
58            mainobj.$control=$('<div id="topcontrol">'+mainobj.controlHTML+'</div>')
59                .css({position:mainobj.cssfixedsupport? 'fixed' : 'absolute', bottom:mainobj.controlattrs.offsety, right:mainobj.controlattrs.offsetx, opacity:0, cursor:'pointer'})
60                .attr({title:'Scroll Back to Top'})
61                .click(function(){mainobj.scrollup(); return false})
62                .appendTo('body')
63            if (document.all && !window.XMLHttpRequest && mainobj.$control.text()!='') //loose check for IE6 and below, plus whether control contains any text
64                mainobj.$control.css({width:mainobj.$control.width()}) //IE6- seems to require an explicit width on a DIV containing text
65            mainobj.togglecontrol()
66            $('a[href="' + mainobj.anchorkeyword +'"]').click(function(){
67                mainobj.scrollup()
68                return false
69            })
70            $(window).bind('scroll resize', function(e){
71                mainobj.togglecontrol()
72            })
73        })
74    }
75}
76
77scrolltotop.init()