带占位符的jQuery自动完成功能

Question

我已嵌入此jQuery自动完成下拉列表：https://jqueryui.com/autocomplete/#combobox

我稍微更改了代码以获得占位符。 这是我的代码：

<select id="provider" name="provider" required="">
   <option value="1">1</option>
   <option value="2">2</option>
   <option value="3">3</option>
</select>

<script>
    $( function() {
    $.widget( "custom.combobox", {
      _create: function() {
        this.wrapper = $( "<span>" )
          .addClass( "custom-combobox" )
          .insertAfter( this.element );

        this.element.hide();
        this._createAutocomplete();
        this._createShowAllButton();
      },

      _createAutocomplete: function() {
        var selected = this.element.children( ":selected" ),
          value = selected.val() ? selected.text() : "";

        this.input = $( "<input>" ).appendTo( this.wrapper ).val( value ).attr( "title", "" ).attr( "placeholder", "My Placeholder" ).addClass("form-control input-md")
          .autocomplete({
            delay: 0,
            minLength: 0,
            source: $.proxy( this, "_source" )
          })
          .tooltip({
            classes: {
              "ui-tooltip": "ui-state-highlight"
            }
          });

        this._on( this.input, {
          autocompleteselect: function( event, ui ) {
            ui.item.option.selected = true;
            this._trigger( "select", event, {
              item: ui.item.option
            });
          },

          autocompletechange: "_removeIfInvalid"
        });
      },


      _source: function( request, response ) {
        var matcher = new RegExp( $.ui.autocomplete.escapeRegex(request.term), "i" );
        response( this.element.children( "option" ).map(function() {
          var text = $( this ).text();
          if ( this.value && ( !request.term || matcher.test(text) ) )
            return {
              label: text,
              value: text,
              option: this
            };
        }) );
      },

      _removeIfInvalid: function( event, ui ) {

        // Selected an item, nothing to do
        if ( ui.item ) {
          return;
        }

        // Search for a match (case-insensitive)
        var value = this.input.val(),
          valueLowerCase = value.toLowerCase(),
          valid = false;
        this.element.children( "option" ).each(function() {
          if ( $( this ).text().toLowerCase() === valueLowerCase ) {
            this.selected = valid = true;
            return false;
          }
        });

        // Found a match, nothing to do
        if ( valid ) {
          return;
        }

        // Remove invalid value
        this.input.val( "" ).attr( "title", "Error" ).tooltip( "open" );this.element.val( "" );
        this._delay(function() {
          this.input.tooltip( "close" ).attr( "title", "" );
        }, 2500 );
        this.input.autocomplete( "instance" ).term = "";
      },

      _destroy: function() {
        this.wrapper.remove();
        this.element.show();
      }
    });

    $( "#provider" ).combobox();
  } );
</script>

问题是，我在加载页面后没有直接获得占位符 - 它将显示我的下拉列表的第一个元素 - 在这种情况下是值＆＃34; 1＆＃34;。 如果我从输入字段中删除文本手册，将显示占位符。有人有点想法吗？ ：）