bootstrap daterangepicker汉化以及扩展功能

/* 扩展该组件：增加一个select */
  var _this = this;

  var selectItem = '<select id="dateranepicker_select" class="form-control width150 inline-block">';
  selectItem += '<option>今日</option>';
  selectItem += '<option>昨日</option>';
  selectItem += '<option selected="selected">最近7日</option>';
  selectItem += '<option>最近15日</option>';
  selectItem += '<option>最近30日</option>';
  selectItem += '<option>本月</option>';
  selectItem += '<option>上月</option>';
  selectItem += '</select>';

  this.element.parent().append(selectItem);

  $(document).on('change','#dateranepicker_select',function(){

   function auto0(num){
    return num>10?num:'0'+num;
   }

   var val = $(this).val();
   var c_start_date = new Date();
   var c_end_date = new Date();
   if(val=='今日'){

   }
   else if(val=='昨日'){
    c_start_date.setDate(c_start_date.getDate()-1);
    c_end_date.setDate(c_end_date.getDate()-1);
   }
   else if(val=='最近7日'){
    c_start_date.setDate(c_start_date.getDate()-7);
    c_end_date.setDate(c_end_date.getDate()-1);
   }
   else if(val=='最近15日'){
    c_start_date.setDate(c_start_date.getDate()-15);
    c_end_date.setDate(c_end_date.getDate()-1);
   }
   else if(val=='最近30日'){
    c_start_date.setDate(c_start_date.getDate()-30);
    c_end_date.setDate(c_end_date.getDate()-1);
   }
   else if(val=='本月'){
    var cyear = c_start_date.getFullYear();
    var cmonth = c_start_date.getMonth();

    c_start_date = new Date(cyear,cmonth,1);
    c_end_date =new Date(cyear+'-'+ (cmonth+1) +'-'+new Date(cyear,cmonth+1,0).getDate());

   }
   else if(val=='上月'){
    var cyear = c_start_date.getFullYear();
    var cmonth = c_start_date.getMonth()-1;
    c_start_date = new Date(cyear,cmonth,1);
    c_end_date =new Date(cyear+'-'+ (cmonth+1) +'-'+new Date(cyear,cmonth+1,0).getDate());
   }
   _this.setStartDate(c_start_date);
   _this.setEndDate(c_end_date);

   timespanStr =auto0(c_start_date.getMonth()+1)+'/'+ auto0(c_start_date.getDate()) + '/'+c_start_date.getFullYear()+'-'+ auto0(c_end_date.getMonth()+1) + '/' +auto0(c_end_date.getDate()) + '/' +c_end_date.getFullYear();

   _this.element.val(timespanStr);
   _this.hide();
   _this.element.trigger('apply.daterangepicker', _this);
   /* 扩展该组件 end */


  });