https://www.du.ac.bd/fontView/assets/js/jquery.appear.js

1/*
2* jQuery.appear
3* https://github.com/bas2k/jquery.appear/
4* http://code.google.com/p/jquery-appear/
5* http://bas2k.ru/
6*
7* Copyright (c) 2009 Michael Hixson
8* Copyright (c) 2012-2014 Alexander Brovikov
9* Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php)
10*/
11(function($) {
12
13    "use strict"
14
15    $.fn.appear = function(fn, options) {
16
17        var settings = $.extend({
18
19            //arbitrary data to pass to fn
20            data: undefined,
21
22            //call fn only on the first appear?
23            one: true,
24
25            // X & Y accuracy
26            accX: 0,
27            accY: 0
28
29        }, options);
30
31        return this.each(function() {
32
33            var t = $(this);
34
35            //whether the element is currently visible
36            t.appeared = false;
37
38            if (!fn) {
39
40                //trigger the custom event
41                t.trigger('appear', settings.data);
42                return;
43            }
44
45            var w = $(window);
46
47            //fires the appear event when appropriate
48            var check = function() {
49
50                //is the element hidden?
51                if (!t.is(':visible')) {
52
53                    //it became hidden
54                    t.appeared = false;
55                    return;
56                }
57
58                //is the element inside the visible window?
59                var a = w.scrollLeft();
60                var b = w.scrollTop();
61                var o = t.offset();
62                var x = o.left;
63                var y = o.top;
64
65                var ax = settings.accX;
66                var ay = settings.accY;
67                var th = t.height();
68                var wh = w.height();
69                var tw = t.width();
70                var ww = w.width();
71
72                if (y + th + ay >= b &&
73                    y <= b + wh + ay &&
74                    x + tw + ax >= a &&
75                    x <= a + ww + ax) {
76
77                        //trigger the custom event
78                        if (!t.appeared) t.trigger('appear', settings.data);
79
80                    } else {
81
82                        //it scrolled out of view
83                        t.appeared = false;
84                    }
85                };
86
87                //create a modified fn with some additional logic
88                var modifiedFn = function() {
89
90                    //mark the element as visible
91                    t.appeared = true;
92
93                    //is this supposed to happen only once?
94                    if (settings.one) {
95
96                        //remove the check
97                        w.unbind('scroll', check);
98                        var i = $.inArray(check, $.fn.appear.checks);
99                        if (i >= 0) $.fn.appear.checks.splice(i, 1);
100                    }
101
102                    //trigger the original fn
103                    fn.apply(this, arguments);
104                };
105
106                //bind the modified fn to the element
107                if (settings.one) t.one('appear', settings.data, modifiedFn);
108                else t.bind('appear', settings.data, modifiedFn);
109
110                //check whenever the window scrolls
111                w.scroll(check);
112
113                //check whenever the dom changes
114                $.fn.appear.checks.push(check);
115
116                //check now
117                (check)();
118            });
119        };
120
121        //keep a queue of appearance checks
122        $.extend($.fn.appear, {
123
124            checks: [],
125            timeout: null,
126
127            //process the queue
128            checkAll: function() {
129                var length = $.fn.appear.checks.length;
130                if (length > 0) while (length--) ($.fn.appear.checks[length])();
131            },
132
133            //check the queue asynchronously
134            run: function() {
135                if ($.fn.appear.timeout) clearTimeout($.fn.appear.timeout);
136                $.fn.appear.timeout = setTimeout($.fn.appear.checkAll, 20);
137            }
138        });
139
140        //run checks when these methods are called
141        $.each(['append', 'prepend', 'after', 'before', 'attr',
142        'removeAttr', 'addClass', 'removeClass', 'toggleClass',
143        'remove', 'css', 'show', 'hide'], function(i, n) {
144            var old = $.fn[n];
145            if (old) {
146                $.fn[n] = function() {
147                    var r = old.apply(this, arguments);
148                    $.fn.appear.run();
149                    return r;
150                }
151            }
152        });
153
154    })(jQuery);