Safariでのみ表示されるSyntaxErrorが見つからない

お世話になっております。
agecheck.jsというJqueryを使用しているのですが、
Safariで確認したときのみ動作しません。

safariの開発者ツールには以下のエラーが出ます。(CHromeではエラーは出ません)

error
1jquery.agecheck.js:57
2SyntaxError: Expected an identifier but found '(' instead
3age.js:7
4TypeError: 'undefined' is not a function (evaluating '$.ageCheck')

該当のコードは以下なのですが、JShintで検証してもエラーはありませんでした。
Syntaxエラーのほかに何か原因があるのかどうかどなたかご教示いただきたいです。

js
1(function ($) {
2  $.ageCheck = function (options) {
3    const settings = $.extend({
4      minAge: 21,
5      redirectTo: '',
6      redirectOnFail: '',
7      success: null,
8      successMsg: {
9        header: '<div id="loading"> <div class="bkimg"><img src="http://XXX/loading.png"></div> <div class="spinner"><img src="http://XXX/test.png"></div></div>',
10        body: ''
11      },
12      underAgeMsg: '年齢確認が出来ませんでした。',
13      underAge: null,
14      errorMsg: {
15        invalidDay: '有効な日付をご入力ください'
16      },
17      storage: 'sessionStorage',
18      storageExpires: null,
19    }, options);
20
21    var storage = window[settings.storage];
22
23    const _this = {
24      month: '',
25      day: '',
26      year: '',
27      age: '',
28      errors: [],
29      setValues() { ★57行目
30        const month = $('.ac-container .month').val();
31        const day = $('.ac-container .days').val();
32        _this.month = month;
33        _this.days = day.replace(/^0+/, ''); // remove leading zero
34        _this.year = $('.ac-container .year').val();
35      },
36      validate() {
37        _this.errors = [];
38        if (!(/^([0-9]|[12]\d|3[0-1])$/.test(_this.days))||!(/^(19|20)\d{2}$/.test(_this.year))||!(/^(0[1-9]|[1-9]|1[0-2])$/.test(_this.month))) {
39          _this.errors.push(settings.errorMsg.invalidDay);
40        }
41
42        _this.clearErrors();
43        _this.displayErrors();
44        return _this.errors.length < 1;
45      },
46      clearErrors() {
47        $('.errors').html('');
48      },
49      displayErrors() {
50        let html = '<ul>';
51        for (let i = 0; i < _this.errors.length; i++) {
52          html += `<li><span>x</span>${_this.errors[i]}</li>`;
53        }
54        html += '</ul>';
55        setTimeout(() => {
56          $('.ac-container .errors').html(html);
57        }, 200);
58      },
59      reCenter(b) {
60        b.css('top', `${Math.max(0, (($(window).height() - (b.outerHeight() + 150)) / 2))}px`);
61        b.css('left', `${Math.max(0, (($(window).width() - b.outerWidth()) / 2))}px`);
62      },
63
64
65      buildHtml() {
66        const copy = settings.copy;
67        let html = '';
68        html += '<div class="ac-overlay"></div>';
69        html += '<div class="ac-container">';
70        html += `<img class="ageCheckImg" src="http://mixintl-stg.kir.jp/20200731_ez/test/img/top/agecheck.png" width="70%">`;
71        html += `<div class="subtitle">${settings.subtitle}</div>`;
72        html += `<h2>${settings.title}</h2>`;
73        html += `<p>${copy.replace('[21]', `<strong >${settings.minAge}</strong>`)}` + '</p>';
74        html += `<div class="errors"></div>`;
75
76        html += '</select>';
77        html += '<input type="number" class="year" placeholder="年(西暦)" min=0 save="" oninput="sliceMaxLength(this, 4)" oninput="validity.valid ? this.save = value : value = this.save;">';
78        html += '<input type="number" class="month" placeholder="月" min=0 save="" oninput="sliceMaxLength(this, 2)" oninput="validity.valid ? this.save = value : value = this.save;">';
79        html += '<input type="number" class="days" placeholder="日" min=0 save="" oninput="sliceMaxLength(this, 2)" oninput="validity.valid ? this.save = value : value = this.save;">';
80        html += '<br><button>年齢確認</button></div>';
81
82        $('body').append(html);
83
84        $('.ac-overlay').animate({
85          opacity: 1,
86        }, 500, () => {
87          _this.reCenter($('.ac-container'));
88          $('.ac-container').css({
89            opacity: 1,
90          });
91        });
92        
93        //フォーカスでプレースホルダ消す 20200812.一旦無効化
94        /*('.ac-container .days, .ac-container .month,.ac-container .year').focus(function () {
95          $(this).removeAttr('placeholder');
96        });*/
97      },
98      setAge() {
99        _this.age = '';
100        const birthday = new Date(_this.year, _this.month, _this.days);
101        const ageDifMs = Date.now() - birthday.getTime();
102        const ageDate = new Date(ageDifMs); // miliseconds from epoch
103        _this.age = Math.abs(ageDate.getUTCFullYear() - 1970);
104      },
105      getStorage() {
106        if(settings.storage === 'cookie') {
107          return document.cookie.split(';').filter((item) => item.trim().startsWith('ageVerified=')).length;
108        } else {
109          return storage.getItem('ageVerified') === 'true';
110        }
111      },
112      setStorage(key, val, expires) {
113        try {
114          if(settings.storage === 'cookie') {
115            if(expires) {
116              let date = new Date();
117              date.setTime(date.getTime() + (expires * 24 * 60 * 60 * 1000));
118              expires = date.toGMTString();
119            }
120            document.cookie = "ageVerified=true; expires=" + expires + ";";
121          } else {
122            storage.setItem(key, val);
123          }
124          return true;
125        } catch (e) {
126          return false;
127        }
128      },
129      handleSuccess() {
130        const successMsg = `<h3>${settings.successMsg.header}</h3><p>${settings.successMsg.body}</p>`;
131        $('.ac-container').html(successMsg);
132        setTimeout(() => {
133          $('.ac-container').animate({
134            top: '-350px',
135          }, 200, () => {
136            $('.ac-overlay').animate({
137              opacity: '0',
138            }, 500, () => {
139              if (settings.redirectTo !== '') {
140                window.location.replace(settings.redirectTo);
141              } else {
142                $('.ac-overlay, .ac-container').remove();
143                if (settings.success) {
144                  settings.success();
145                }
146              }
147            });
148          });
149        }, 2000);
150      },
151      handleUnderAge() {
152        const underAgeMsg = `<div class="underAgeMsg">${settings.underAgeMsg}</div>`;
153        $('.ac-container').html(underAgeMsg);
154        if (settings.redirectOnFail !== '') {
155          setTimeout(() => {
156            window.location.replace(settings.redirectOnFail);
157          }, 2000);
158        }
159        if (settings.underAge) {
160          settings.underAge();
161        }
162      },
163    }; // end _this
164
165    if (_this.getStorage()) {
166      return false;
167    }
168
169    _this.buildHtml();
170
171    $('.ac-container button').on('click', () => {
172      _this.setValues();
173      if (_this.validate() === true) {
174        _this.setAge();
175
176        if (_this.age >= settings.minAge) {
177          if (!_this.setStorage('ageVerified', 'true', settings.storageExpires)) {
178            console.log(settings.storage + ' not supported by your browser');
179          }
180          _this.handleSuccess();
181        } else {
182          _this.handleUnderAge();
183        }
184      }
185    });
186
187    $(window).resize(() => {
188      _this.reCenter($('.ac-container'));
189      setTimeout(() => {
190        _this.reCenter($('.ac-container'));
191      }, 500);
192    });
193  };
194}(jQuery));