https://teenhealthandwellness.com/js/third-party/jquery-ext.js

1(function ($) {
2    $.fn.down = function () {
3        var el = this[0] && this[0].firstChild;
4        while (el && el.nodeType != 1)
5            el = el.nextSibling;
6        return $(el);
7    };
8    $.fn.exists = function () {
9        return this.length !== 0;
10    };
11    if (!String.prototype.endsWith) {
12        Object.defineProperty(String.prototype, 'endsWith', {
13            value: function (searchString, position) {
14                var subjectString = this.toString();
15                if (position === undefined || position > subjectString.length) {
16                    position = subjectString.length;
17                }
18                position -= searchString.length;
19                var lastIndex = subjectString.indexOf(searchString, position);
20                return lastIndex !== -1 && lastIndex === position;
21            }
22        });
23    }
24    if (!Array.prototype.includes) {
25        Object.defineProperty(Array.prototype, 'includes', {
26            value: function (searchElement, fromIndex) {
27
28                if (this == null) {
29                    throw new TypeError('"this" is null or not defined');
30                }
31
32                // 1. Let O be ? ToObject(this value).
33                var o = Object(this);
34
35                // 2. Let len be ? ToLength(? Get(O, "length")).
36                var len = o.length >>> 0;
37
38                // 3. If len is 0, return false.
39                if (len === 0) {
40                    return false;
41                }
42
43                // 4. Let n be ? ToInteger(fromIndex).
44                //    (If fromIndex is undefined, this step produces the value 0.)
45                var n = fromIndex | 0;
46
47                // 5. If n ≥ 0, then
48                //  a. Let k be n.
49                // 6. Else n < 0,
50                //  a. Let k be len + n.
51                //  b. If k < 0, let k be 0.
52                var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
53
54                function sameValueZero(x, y) {
55                    return x === y || (typeof x === 'number' && typeof y === 'number' && isNaN(x) && isNaN(y));
56                }
57
58                // 7. Repeat, while k < len
59                while (k < len) {
60                    // a. Let elementK be the result of ? Get(O, ! ToString(k)).
61                    // b. If SameValueZero(searchElement, elementK) is true, return true.
62                    if (sameValueZero(o[k], searchElement)) {
63                        return true;
64                    }
65                    // c. Increase k by 1.
66                    k++;
67                }
68
69                // 8. Return false
70                return false;
71            }
72        });
73    }
74})(jQuery);