https://worldlinedancenewsletter.com/js/scrolltopcontrol.js

1//** jQuery Scroll to Top Control script- (c) Dynamic Drive DHTML code library: https://www.dynamicdrive.com.
2//** Available/ usage terms at https://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:40, scrollto: 0, scrollduration:200, fadeduration:[500, 100]},
12	controlHTML: '<img src="img/ship2top.png" class="backtotop" />', //HTML for control, which is auto wrapped in DIV w/ ID="topcontrol"
13	controlattrs: {offsetx:16, offsety:12}, //offset of control relative to right/ bottom of window corner
14	anchorkeyword: '#logo', //Enter href value of HTML anchors on the page that should also act as "Scroll Up" links
15
16	state: {isvisible:false, shouldvisible:false},
17
18	scrollup:function(){
19		if (!this.cssfixedsupport) //if control is positioned using JavaScript
20			this.$control.css({opacity:0}) //hide control immediately after clicking it
21		var dest=isNaN(this.setting.scrollto)? this.setting.scrollto : parseInt(this.setting.scrollto)
22		if (typeof dest=="string" && jQuery('#'+dest).length==1) //check element set by string exists
23			dest=jQuery('#'+dest).offset().top
24		else
25			dest=0
26		this.$body.animate({scrollTop: dest}, this.setting.scrollduration);
27	},
28
29	keepfixed:function(){
30		var $window=jQuery(window)
31		var controlx=$window.scrollLeft() + $window.width() - this.$control.width() - this.controlattrs.offsetx
32		var controly=$window.scrollTop() + $window.height() - this.$control.height() - this.controlattrs.offsety
33		this.$control.css({left:controlx+'px', top:controly+'px'})
34	},
35
36	togglecontrol:function(){
37		var scrolltop=jQuery(window).scrollTop()
38		if (!this.cssfixedsupport)
39			this.keepfixed()
40		this.state.shouldvisible=(scrolltop>=this.setting.startline)? true : false
41		if (this.state.shouldvisible && !this.state.isvisible){
42			this.$control.stop().animate({opacity:1}, this.setting.fadeduration[0])
43			this.state.isvisible=true
44		}
45		else if (this.state.shouldvisible==false && this.state.isvisible){
46			this.$control.stop().animate({opacity:0}

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