HerokuへのPush時にエラーが出てしまう。

前提・実現したいこと

・HerokuへPushすること

発生している問題・エラーメッセージ

【問題】
開発環境では問題なく動いていたプログラムを
HerokuへPushしようとしたところ、以下のエラーを生じてしまいました。

エラーメッセージ

ec2
1Counting objects: 69, done.
2Compressing objects: 100% (68/68), done.
3Writing objects: 100% (69/69), 7.79 KiB | 1.11 MiB/s, done.
4Total 69 (delta 54), reused 0 (delta 0)
5remote: Compressing source files... done.
6remote: Building source:
7remote: 
8remote: -----> Ruby app detected
9remote: -----> Installing bundler 1.17.3
10remote: -----> Removing BUNDLED WITH version in the Gemfile.lock
11remote: -----> Compiling Ruby/Rails
12remote: -----> Using Ruby version: ruby-2.6.5
13remote: -----> Installing dependencies using bundler 1.17.3
14remote:        Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
15remote:        The dependency tzinfo-data (>= 0) will be unused by any of the platforms Bundler is installing for. Bundler is installing for ruby but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
16【中略】
17platforms Bundler is installing for. Bundler is installing for ruby but the dependency is only for x86-mingw32, x86-mswin32, x64-mingw32, java. To add those platforms to the bundle, run `bundle lock --add-platform x86-mingw32 x86-mswin32 x64-mingw32 java`.
18remote: -----> Installing node-v10.15.3-linux-x64
19remote: -----> Detecting rake tasks
20remote: -----> Preparing app for Rails asset pipeline
21remote:        Running: rake assets:precompile
22remote:        Yarn executable was not detected in the system.
23remote:        Download Yarn at https://yarnpkg.com/en/docs/install
24remote:        rake aborted!
25remote:        ExecJS::RuntimeError: SyntaxError: Invalid assignment
26remote:        /tmp/build_ff59ef4dc7d429a0c92e7c5996b87f2c/app/assets/config/manifest.js:2
27remote:        JS_Parse_Error.get ((execjs):3538:621)
28remote:        (execjs):4060:48
29remote:        (execjs):1:102
30remote:        Object.<anonymous> ((execjs):1:120)
31remote:        Module._compile (internal/modules/cjs/loader.js:701:30)
32remote:        Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10
33remote:        Module.load (internal/modules/cjs/loader.js:600:32)
34remote:        tryModuleLoad (internal/modules/cjs/loader.js:539:12)
35remote:        Function.Module._load (internal/modules/cjs/loader.js:531:3)
36remote:        Function.Module.runMain (internal/modules/cjs/loader.js:754:12)
37【略】
38
39To https://git.heroku.com/lecceed.git
40 ! [remote rejected] master -> master (pre-receive hook declined)
41error: failed to push some refs to 'https://git.heroku.com/lecceed.git'
42
43### 該当のソースコード
44$(document).on('turbolinks:load', function(){
45  $('.fa-list').click(function() {
46    $('.ladder-menu').fadeIn();
47    $(this).css('display', 'none');
48    $('.fa-times').css('display', 'block')
49  });
50  
51  $('.fa-times').click(function(){
52    $('.ladder-menu').fadeOut();
53    $(this).css('display', 'none');
54    $('.fa-list').css('display', 'block')
55  });
56  
57  $('.open').click(function() {
58    $(this).hide();
59    $(this).nextAll('.favo-items').slideDown();
60    $(this).next('.close').show();
61  })
62  
63  $('.close').click(function() {
64    $(this).hide();
65    $(this).nextAll('.favo-items').slideUp();
66    $(this).prev('.open').show();
67  })
68  
69   $('.rateYo-understanding').rateYo({
70    starWidth: "20px",
71    rating: Number($(".rateYo-understanding").data('star')),
72    halfStar: true,
73    readOnly: true,
74    ratedFill: '#2AC926'
75  });
76  
77  $('.rateYo-getting').rateYo({
78    starWidth: "20px",
79    rating: Number($(".rateYo-getting").data('star')),
80    halfStar: true,
81    readOnly: true,
82    ratedFill: '#2AC926'
83  });
84  
85  $('.rateYo-interest').rateYo({
86    starWidth: "20px",
87    rating: Number($(".rateYo-interest").data('star')),
88    halfStar: true,
89    readOnly: true,
90    ratedFill: '#2AC926'
91  });
92  
93  $('.rateYo-all').rateYo({
94    starWidth: "25px",
95    rating: Number($(".rateYo-all").data('star')),
96    halfStar: true,
97    readOnly: true,
98    ratedFill: '#FF3D00'
99  });
100  
101  $('.rateYo-all-lectures').rateYo({
102    starWidth: "18px",
103    rating: Number($(".rateYo-all-lectures").data('star')),
104    halfStar: true,
105    readOnly: true,
106    ratedFill: '#FF3D00'
107  });
108  
109  
110
111  
112  var bar = new ProgressBar.Line(container, {
113    strokeWidth: 4,
114    easing: 'easeInOut',
115    duration: 1400,
116    color: '#FFEA82',
117    trailColor: '#eee',
118    trailWidth: 3,
119    svgStyle: {width: '100%', height: '100%'},
120    from: {color: '#6DACE5'},
121    to: {color: '#057FF0'},
122    step: (state, bar) => {
123      bar.path.setAttribute('stroke', state.color);
124    }
125  });
126
127  bar.animate($("#container").data('progress'));  // Number from 0.0 to 1.0
128  
129  var bare = new ProgressBar.Line(condtainer, {
130    strokeWidth: 4,
131    easing: 'easeInOut',
132    duration: 1400,
133    color: '#FFEA82',
134    trailColor: '#eee',
135    trailWidth: 3,
136    svgStyle: {width: '100%', height: '100%'},
137    from: {color: '#6DACE5'},
138    to: {color: '#057FF0'},
139    step: (state, bare) => {
140      bare.path.setAttribute('stroke', state.color);
141    }
142  });
143
144  bare.animate($("#condtainer").data('progressed'));  // Number from 0.0 to 1.0
145  
146  
147})
148```ここに言語を入力
149