jsでのカスタムデータの取得について

現在メモアプリを作成しているのですが、haml側のカスタムデータをjsで取得しようとするとundefinedが返ってくる。

haml
1%header
2  .header__main
3    %h1.title Memo-calendar
4    .change
5      .account
6        = link_to edit_user_path(current_user) do
7          = icon('fas', 'cog', class: 'icon')
8.main
9  .sidememo
10    .sidememo__bar
11      .sidememo__bar__plus
12        %i.icon.fas.fa-plus
13      .sidememo__bar__bars
14        %i.icon.fas.fa-bars
15    .sidememo__space
16      %ul#memo-box
17        %div#memo-input
18          %label.date{date:{label_id: 0 }}
19  .front
20    .calendar
21      .calendar__main{style:"border-left-style: hidden;"}
22      .calendar__tool
23    .memo
24      .memo__main
25        .memo__main__day
26          .memo__main__day__bar
27            .memo__main__day__bar__eye
28              %i.icon.far.fa-eye
29            .memo__main__day__bar__bars
30              %i.icon.fas.fa-bars
31          .memo__main__day__space
32      .memo__side

js
1$(document).on('turbolinks:load', function(){
2  // クリック時side-memoの追加
3  $(document).on('click','.sidememo__bar__plus', function(){
4
5    let labelLength = $("#memo-input>label").data('label-id');
6    console.log(`${labelLength}`)
7
8    $("#memo-input").before(`<li class="side-memo" id="write-memo${labelLength}" date-smemo-id="${labelLength}">
9                              <div class="memo-preview${labelLength}">
10                                <div class="memo-preview__bar">
11                                  <input class="memo-preview__bar__title" type="text" >
12                                  <div class="memo-preview__bar__times" date-smemo-id="${labelLength}">
13                                    <i class="fas fa-times" ></i>
14                                  </div>
15                                </div>
16                                <div class="memo-preview__text">
17                                  <textarea class="memo-preview__text__main"></textarea>
18                                </div>
19                              </div>
20                            </li>`)
21  });
22  
23  $('#memo-box').on('click','.memo-preview__bar__times', function(){
24    let targetSmemoId = $(this).data(`smemo-id`);
25    console.log(`${targetSmemoId}`)
26    $(`#write-memo${targetSmemoId}`).remove();
27  });
28});