计算指定日期加天数后的日期

要求：查询指定日期的0时开始，加天数得到日期的23：59:59

/**

* 结课日期
* startDate 开课日期
* valueTime 
* var stringTime = "2017-11-27 0:0:0";
console.log(lessonEndingDate(stringTime,100))
*/
function lessonEndingDate(startDate,valueTime){  
var date = new Date(startDate);  
var newDate = new Date(date.getFullYear(),date.getMonth(),date.getDate()+valueTime+1,date.getHours(),date.getMinutes(),date.getSeconds()-1);  
var year = newDate.getFullYear();  
var month = newDate.getMonth()+1;  
var day = newDate.getDate();  
var h = newDate.getHours();  
var m = newDate.getMinutes();  
var s = newDate.getSeconds();  
return   year+"-"+month+"-"+day+" "+h+":"+m+":"+s;
  
}