1+ if ( ! String . prototype . endsWith ) {
2+ String . prototype . endsWith = function ( search , this_len ) {
3+ if ( this_len === undefined || this_len > this . length ) {
4+ this_len = this . length ;
5+ }
6+ return this . substring ( this_len - search . length , this_len ) === search ;
7+ } ;
8+ }
9+ if ( ! String . prototype . startsWith ) {
10+ Object . defineProperty ( String . prototype , 'startsWith' , {
11+ value : function ( search , pos ) {
12+ pos = ! pos || pos < 0 ? 0 : + pos ;
13+ return this . substring ( pos , pos + search . length ) === search ;
14+ }
15+ } ) ;
16+ }
17+ if ( ! String . prototype . includes ) {
18+ String . prototype . includes = function ( search , start ) {
19+ 'use strict' ;
20+ if ( typeof start !== 'number' ) {
21+ start = 0 ;
22+ }
23+
24+ if ( start + search . length > this . length ) {
25+ return false ;
26+ } else {
27+ return this . indexOf ( search , start ) !== - 1 ;
28+ }
29+ } ;
30+ }
31+ // https://tc39.github.io/ecma262/#sec-array.prototype.find
32+ if ( ! Array . prototype . find ) {
33+ Object . defineProperty ( Array . prototype , 'find' , {
34+ value : function ( predicate ) {
35+ // 1. Let O be ? ToObject(this value).
36+ if ( this == null ) {
37+ throw new TypeError ( '"this" is null or not defined' ) ;
38+ }
39+
40+ var o = Object ( this ) ;
41+
42+ // 2. Let len be ? ToLength(? Get(O, "length")).
43+ var len = o . length >>> 0 ;
44+
45+ // 3. If IsCallable(predicate) is false, throw a TypeError exception.
46+ if ( typeof predicate !== 'function' ) {
47+ throw new TypeError ( 'predicate must be a function' ) ;
48+ }
49+
50+ // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
51+ var thisArg = arguments [ 1 ] ;
52+
53+ // 5. Let k be 0.
54+ var k = 0 ;
55+
56+ // 6. Repeat, while k < len
57+ while ( k < len ) {
58+ // a. Let Pk be ! ToString(k).
59+ // b. Let kValue be ? Get(O, Pk).
60+ // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
61+ // d. If testResult is true, return kValue.
62+ var kValue = o [ k ] ;
63+ if ( predicate . call ( thisArg , kValue , k , o ) ) {
64+ return kValue ;
65+ }
66+ // e. Increase k by 1.
67+ k ++ ;
68+ }
69+
70+ // 7. Return undefined.
71+ return undefined ;
72+ } ,
73+ configurable : true ,
74+ writable : true
75+ } ) ;
76+ }
77+
78+ // From https://github.com/kevlatus/polyfill-array-includes/blob/master/array-includes.js
79+ if ( ! Array . prototype . includes ) {
80+ Object . defineProperty ( Array . prototype , 'includes' , {
81+ value : function ( searchElement , fromIndex ) {
82+
83+ // 1. Let O be ? ToObject(this value).
84+ if ( this == null ) {
85+ throw new TypeError ( '"this" is null or not defined' ) ;
86+ }
87+
88+ var o = Object ( this ) ;
89+
90+ // 2. Let len be ? ToLength(? Get(O, "length")).
91+ var len = o . length >>> 0 ;
92+
93+ // 3. If len is 0, return false.
94+ if ( len === 0 ) {
95+ return false ;
96+ }
97+
98+ // 4. Let n be ? ToInteger(fromIndex).
99+ // (If fromIndex is undefined, this step produces the value 0.)
100+ var n = fromIndex | 0 ;
101+
102+ // 5. If n ≥ 0, then
103+ // a. Let k be n.
104+ // 6. Else n < 0,
105+ // a. Let k be len + n.
106+ // b. If k < 0, let k be 0.
107+ var k = Math . max ( n >= 0 ? n : len - Math . abs ( n ) , 0 ) ;
108+
109+ function sameValueZero ( x , y ) {
110+ return x === y || ( typeof x === 'number' && typeof y === 'number' && isNaN ( x ) && isNaN ( y ) ) ;
111+ }
112+
113+ // 7. Repeat, while k < len
114+ while ( k < len ) {
115+ // a. Let elementK be the result of ? Get(O, ! ToString(k)).
116+ // b. If SameValueZero(searchElement, elementK) is true, return true.
117+ // c. Increase k by 1.
118+ if ( sameValueZero ( o [ k ] , searchElement ) ) {
119+ return true ;
120+ }
121+ k ++ ;
122+ }
123+
124+ // 8. Return false
125+ return false ;
126+ }
127+ } ) ;
128+ }
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