事象 : プルダウンリストの選択肢が消える

原因 : bootstrap-selectより後に`option`タグを作るから

htmlでbootstrap-select.min.jsの後に<option>タグを作るmyBootstrapSelect.jsを読み込んでいるのが原因。

<!DOCTYPE html>
<html>
<head>
    <title>bootstrap-selectで作るプルダウン</title>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.4/css/bootstrap-select.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.4/js/bootstrap-select.min.js"></script>
    <script type="text/javascript" src="js/myBootstrapSelect.js"></script>
</head>
<body>
    <select id="targetSelect" size="1" class="selectpicker"></select>
</body>
</html>

myBootstrapSelect.js

var selectOptionCount = 3;

$(window).on('load', function() {
    createSelectOption();
});

function createSelectOption() {
    var selectObj = $('#targetSelect');

    for (var i = 0; i < selectOptionCount; i++) {
        var option = $('<option>');
        option.html(i);
        selectObj.append(option);
    }
}

原因2 : Bootstrap4を使っているのにPopper.jsがないから

環境
- CentOS Linux release 7.8.2003 (Core)
- openjdk version "11.0.7" 2020-04-14 LTS
- JSF 2.3.9
- jquery 3.2.1
- bootstrap 4.3.1
- bootstrap-select 1.13.14

<!--省略-->
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" />
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/css/bootstrap-select.min.css" />
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/js/bootstrap-select.min.js"></script>
<!--省略-->
  <ui:remove>セレクトボックス</ui:remove>
  <h:selectOneMenu id="select" styleClass="selectpicker" value="#{sampleBean.selected}">
    <f:selectItems value="#{sampleBean.selectItems}" />
  </h:selectOneMenu>
<!--省略-->

出力されたHTMLにはちゃんと選択肢があるのに・・・・

<div class="dropdown bootstrap-select">
  <select id="formId:select" name="formId:select" class="selectpicker" size="1" tabindex="-98">    <option value="0">   </option>
    <option value="1">いぬ</option>
    <option value="2">ねこ</option>
    <option value="3">さる</option>
    <option value="4">ぽんすけ</option>
  </select>
  <button type="button" class="btn dropdown-toggle btn-light" data-toggle="dropdown" role="combobox" aria-owns="bs-select-1" aria-haspopup="listbox" aria-expanded="false" data-id="formId:select" title="Nothing selected"><div class="filter-option"><div class="filter-option-inner"><div class="filter-option-inner-inner">Nothing selected</div></div> </div></button>
  <div class="dropdown-menu " style="max-height: 955px; overflow: hidden; min-height: 104px;">
    <div class="inner show" role="listbox" id="bs-select-1" tabindex="-1" aria-activedescendant="bs-select-1-0" style="max-height: 939px; overflow-y: auto; min-height: 88px;">
      <ul class="dropdown-menu inner show" role="presentation" style="margin-top: 0px; margin-bottom: 0px;">
        <li class="selected active"><a role="option" class="dropdown-item active selected" id="bs-select-1-0" tabindex="0" aria-setsize="5" aria-posinset="1" aria-selected="true"><span class="text">   </span></a></li>
        <li><a role="option" class="dropdown-item" id="bs-select-1-1" tabindex="0"><span class="text">いぬ</span></a></li>
        <li><a role="option" class="dropdown-item" id="bs-select-1-2" tabindex="0"><span class="text">ねこ</span></a></li>
        <li><a role="option" class="dropdown-item" id="bs-select-1-3" tabindex="0"><span class="text">さる</span></a></li>
        <li><a role="option" class="dropdown-item" id="bs-select-1-4" tabindex="0"><span class="text">ぽんすけ</span></a></li>
      </ul>
    </div>
  </div>
</div>

と思ったらドキュメントに「Bootstrap v4以降はPopper.jsが必要だよ」ってちゃんと書いてあった。

If using bootstrap-select with Bootstrap v4+, you'll also need Popper.js.
Getting Started | bootstrap-select · SnapAppointments Developer

対応 : Popper.jsを読み込む

<!--省略-->
<!--↓↓追加↓↓-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"></script>
<!--省略-->

事象 : プルダウンリスト外に選択肢が出ている

原因 : `bootstrap.min.css`を読み込んでいないから

<!DOCTYPE html>
<html>
<head>
    <title>bootstrap-selectで作るプルダウン</title>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.4/css/bootstrap-select.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
    <script type="text/javascript" src="js/myBootstrapSelect.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.4/js/bootstrap-select.min.js"></script>
</head>
<body>
    <select id="targetSelect" size="1" class="selectpicker"></select>
</body>
</html>