Detailed explanation of how to use bootstrap drop-down search plug-in

<link rel="stylesheet" href="css/bootstrap-select.css" rel="external nofollow" >

<select class="selectpicker" data-live-search="true" id="d1">
  <option value="-1">请选择</option>
  <option value="0">0</option>
  <option value="1">1</option>
  <option value="2">2</option>
  <option value="3">3</option>
</select>
<select class="selectpicker" data-live-search="true" id="d2">
  <option value="-1">请选择</option>
</select>

function smallScreen(){   // 个人项目中间距处理，可以省略
  if($(window).width()<768){
    $(&#39;.bootstrap-select:not([class*="col-"]):not([class*="form-control"]):not(.input-group-btn)&#39;).css({
      &#39;width&#39;:&#39;100%&#39;,
      &#39;margin-top&#39;:&#39;10px&#39;
    });
  }
}
$(function(){
var erji=[
    [&#39;海淀区&#39;,&#39;东城区&#39;,&#39;西城区&#39;], // 0
    [&#39;浦东区&#39;,&#39;金山区&#39;,&#39;黄埔区&#39;], // 1
    [&#39;台州市&#39;,&#39;杭州市&#39;,&#39;宁波市&#39;,&#39;嘉兴市&#39;], // 2
    [&#39;郑州市&#39;,&#39;洛阳市&#39;,&#39;开封市&#39;] // 3
  ];
  var yuan = &#39;<li src-index="-1" class>&#39; +   // 字符串拼接
      &#39;<a tabindex="0" data-tokens="null" role="option" aria-disabled="false" aria-selected="false">&#39; +
      &#39;<span class="text">请选择</span>&#39; +
      &#39;<span class="glyphicon glyphicon-ok check-mark"></span>&#39; +
      &#39;</a>&#39; +
      &#39;</li>&#39;;
  $(&#39;#d1&#39;).change(function(){  // 一级下拉菜单选项改变事件
    if($(this).val() === &#39;-1&#39;){
      $(&#39;#d2&#39;).prev(&#39;p.dropdown-menu&#39;).find(&#39;ul&#39;).html(yuan);
      $(&#39;#d2&#39;).html(&#39;<option>请选择</option>&#39;);
      $(&#39;.selectpicker&#39;).selectpicker(&#39;refresh&#39;);
      smallScreen();
      return;
    }
    var cityIndex = erji[ this.value ]; // 当前下标在二级对应内容
    var html = &#39;<li src-index="-1" class>&#39; +   // 下拉搜索动态加载成的标签
        &#39;<a tabindex="0" data-tokens="null" role="option" aria-disabled="false" aria-selected="false">&#39; +
        &#39;<span class="text">请选择</span>&#39; +
        &#39;<span class="glyphicon glyphicon-ok check-mark"></span>&#39; +
        &#39;</a>&#39; +
        &#39;</li>&#39;;
    var erjiOption = &#39;<option value="0">请选择</option>&#39;;  // 同事添加option
    for(var i = 0;i<cityIndex.length;i++){
      html+= &#39;<li src-index=&#39;+i+&#39;>&#39; +
          &#39;<a tabindex="0" data-tokens="null" role="option" aria-disabled="false" aria-selected="false">&#39; +
          &#39;<span class="text">&#39;+cityIndex[i]+&#39;</span>&#39; +
          &#39;<span class="glyphicon glyphicon-ok check-mark"></span>&#39; +
          &#39;</a>&#39; +
          &#39;</li>&#39;;  // 此处为了兼容ie，采用的字符串拼接而不是ES6的模板字符串。
      // 添加option
      erjiOption += &#39;<option value=&#39;+i+&#39;>&#39;+cityIndex[i]+&#39;</option>&#39;;
    }
    $(&#39;#d2&#39;).prev(&#39;p.dropdown-menu&#39;).find(&#39;ul&#39;).html(html);
    $(&#39;#d2&#39;).html(erjiOption);
    $(&#39;.selectpicker&#39;).selectpicker(&#39;refresh&#39;);
    smallScreen();
  });
});
});