https://www.asia-p.co.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		smoothing: 'easeInOutExpo'	// MTL KAZ: added
13	},
14	controlHTML: 'ページTOPへ', //HTML for control, which is auto wrapped in DIV w/ ID="topcontrol"
15	controlattrs: {offsetx:20, offsety:30}, //offset of control relative to right/ bottom of window corner
16	anchorkeyword: '#page', //Enter href value of HTML anchors on the page that should also act as "Scroll Up" links
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, this.setting.smoothing);
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.$control.css({left:controlx+'px', top:controly+'px'})
35	},
36
37	togglecontrol:function(){
38		var scrolltop=jQuery(window).scrollTop()
39		if (!this.cssfixedsupport)
40			this.keepfixed()
41		else {			// MTL KAZ: added
42			var documentHeight = jQuery(document).height();
43			var viewHeight = jQuery(window).height()
44			var footerHeight = jQuery("#colophon").height();
45			var height = documentHeight-viewHeight-footerHeight - 30
46			if (jQuery(window).scrollTop() > height)
47				jQuery('#topcontrol').css('bottom',(jQuery(window).scrollTop()-height)+'px');
48			else
49				jQuery('#topcontrol').css('bottom','30px');
50		}
51		this.state.shouldvisible=(scrolltop>=this.setting.startline)? true : false
52		if (this.state.shouldvisible && !this.state.isvisible){
53			this.$control.stop().animate({opacity:1}, this.setting.fadeduration[0])
54			this.state.isvisible=true
55		}
56		else if (this.state.shouldvisible==false && this.state.isvisible){
57			this.$control.stop().animate({opacity:0}

57, this.setting.fadeduration[1])
58			this.state.isvisible=false
59		}
60	},
61	
62	init:function(){
63		jQuery(document).ready(function($){
64			var mainobj=scrolltotop
65			var iebrws=document.all
66			mainobj.cssfixedsupport=!iebrws || iebrws && document.compatMode=="CSS1Compat" && window.XMLHttpRequest //not IE or IE7+ browsers in standards mode
67			mainobj.$body=(window.opera)? (document.compatMode=="CSS1Compat"? $('html') : $('body')) : $('html,body')
68			mainobj.$control=$('<div id="topcontrol">'+mainobj.controlHTML+'</div>')
69				.css({position:mainobj.cssfixedsupport? 'fixed' : 'absolute', bottom:mainobj.controlattrs.offsety, right:mainobj.controlattrs.offsetx, opacity:0, cursor:'pointer'})
70				.attr({title:'ページTOPへ'})
71				.click(function(){mainobj.scrollup(); return false})
72				.appendTo('body')
73			if (document.all && !window.XMLHttpRequest && mainobj.$control.text()!='') //loose check for IE6 and below, plus whether control contains any text
74				mainobj.$control.css({width:mainobj.$control.width()}) //IE6- seems to require an explicit width on a DIV containing text
75			mainobj.togglecontrol()
76			$('a[href="' + mainobj.anchorkeyword +'"]').click(function(){
77				mainobj.scrollup()
78				return false
79			})
80			$(window).bind('scroll resize', function(e){
81				mainobj.togglecontrol()
82			})
83		})
84	}
85}
86
87scrolltotop.init()