jquery无限极联动【地区】

<select name="region[]"  class="region" >            
            <option value="">--请选择--</option>
            <?php foreach ($region_data as $k => $val): ?>
            <option value="<?php echo $val->region_id?>"><?php echo $val->region_name?></option>
            <?php endforeach ?>    
</select>    

<script>
        $(function(){
         $(document).on('change','.region',function(){
            var  region_id=$(this).val();
            var _this=$(this);
            if (region_id<0) {
                _this.nextAll().remove();
                return false;
            }
            $.post('publish_position',{'region_id':region_id},function(msg){
                console.log(msg);
                if (msg.length>0) {
                      str='<select name="region[]" class="region">';
                      str+='<option value="-1">--请选择--</option>';
                       $(msg).each(function(k,v){
                        str+='<option value='+v.region_id+'>'+v.region_name+'</option>';
                       }) 
                       str+='</select>'

                       _this.nextAll().remove();
                       _this.after(str);
                }


            },"json")

          }) 
    })
</script>