jquery获取select的多个选中值

下面的控件可以选择多个select的值

<select multiple="" class="chosen-select form-control" name="assistantDirectorIds" id="assistantDirectorIds"  data-placeholder="请选择..."></select>

如下效果 

    下面的方法是获取select中的text，以“,”间隔拼接出来

          var options = $("#assistantDirectorIdsoption:selected");

          var assistantName = "";

          if(options.length>0){

              for (var i=0;i<options.length;i++){

                  assistantName += options[i].text;

                  assistantName += ","

             }

             assistantName =assistantName.substr(0,assistantName.length-1);

             $("#assistantDirector").val(assistantName);