https://www.dentimedshop.cz/lib/js/viewport/scrolltopcntrl.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: '<i class="fa fa-arrow-circle-up btnHome hvr-grow scroll-to-top"></i>', //HTML for control, which is auto wrapped in DIV w/ ID="topcontrol"
13    controlattrs: {offsetx: 5, offsety: 5}, //offset of control relative to right/ bottom of window corner
14    anchorkeyword: '#top', //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        } else if (this.state.shouldvisible == false && this.state.isvisible) {
45            this.$control.stop().animate({opacity: 0}, this.setting.fadeduration[1])
46            this.state.isvisible = false
47        }
48    },
49
50    init: function () {
51        jQuery(document).ready(function ($) {
52            var mainobj = scrolltotop
53            var iebrws = document.all
54            mainobj.cssfixedsupport = !iebrws || iebrws && document.compatMode == "CSS1Compat" && window.XMLHttpRequest //not IE or IE7+ browsers in standards mode
55            mainobj.$body = (window.opera) ? (document.compatMode == "CSS1Compat" ? $('html') : $('body')) : $('html,body')
56            mainobj.$control = $('<div id="topcontrol">' + mainobj.controlHTML + '</div>')
57                .css({
58                    position: mainobj.cssfixedsupport ? 'fixed' : 'absolute',
59                    bottom: mainobj.controlattrs.offsety,
60                    right: mainobj.controlattrs.offsetx,
61                    opacity: 0,
62                    cursor: 'pointer'
63                })
64                .attr({title: ''})
65                .click(function () {
66                    mainobj.scrollup();
67                    return false
68                })
69                .appendTo('body')
70            if (document.all && !window.XMLHttpRequest && mainobj.$control.text() != '') //loose check for IE6 and below, plus whether control contains any text
71                mainobj.$control.css({width: mainobj.$control.width()}) //IE6- seems to require an explicit width on a DIV containing text
72            mainobj.togglecontrol()
73            $('a[href="' + mainobj.anchorkeyword + '"]').click(function () {
74                mainobj.scrollup()
75                return false
76            })
77            $(window).bind('scroll resize', function (e) {
78                mainobj.togglecontrol()
79            })
80        })
81    }
82}
83
84scrolltotop.init()