js时间戳转换日期格式和日期计算

 1 function formatDate(datetime) {
 2         // 获取年月日时分秒值  slice(-2)过滤掉大于10日期前面的0
 3         var year = datetime.getFullYear(),
 4             month = ("0" + (datetime.getMonth() + 1)).slice(-2),
 5             date = ("0" + datetime.getDate()).slice(-2),
 6             hour = ("0" + datetime.getHours()).slice(-2),
 7             minute = ("0" + datetime.getMinutes()).slice(-2),
 8             second = ("0" + datetime.getSeconds()).slice(-2);
 9         // 拼接
10         var result = year + "-"+ month +"-"+ date +" "+ hour +":"+ minute +":" + second;
11         // 返回
12         return result;
13     }
14 
15     var date = new Date();
16     console.log(formatDate(date)); // 2018-05-26 23:09:26

 1 //date： 日期字符串yyyy-MM-dd，如：2016-02-14
 2 //years：年份，正整数字符串
 3 //返回日期字符串yyyy-MM-dd，如：2016-02-14
 4     function dateAddYear(date, years) {
 5         var now = new Date(date);
 6         var intYear = now.getFullYear() + parseInt(years);
 7         var intMonth = now.getMonth() + 1; //正常的月份，
 8         var intDay = now.getDate() - 1; //日期-1
 9         if (intDay == 0) {
10             intMonth--; //减少一个月
11             if (intMonth == 0) {
12                 intYear--; //0:减少一年
13                 intMonth = 12;
14                 intDay = 31;
15             }
16             else if (intMonth == 4 || intMonth == 6 || intMonth == 9 || intMonth == 11) {
17                 intDay = 30; //4,6,9,11:30天
18             }
19             else if (intMonth == 2) {
20                 intDay = 28; //2:28/29
21                 if (intYear % 4 == 0) {
22                     intDay = 29;
23                 }
24             } else {
25                 intDay = 31; //1,3,5,7,8,10,12 :31天
26             }
27         }
28 
29         var strMonth = (intMonth) < 10 ? "0" + (intMonth).toString() : (intMonth).toString();
30         var strDay = (intDay) < 10 ? "0" + (intDay).toString() : (intDay).toString();
31         var strEndDate = intYear + "-" + strMonth + "-" + strDay;
32         return strEndDate;
33     }
34     
35     console.log(dateAddYear('2018-6-10','2')); //  2020-06-09

 1 function calculateDate(beginDate,count){
 2         var date = new Date(beginDate);
 3         date.setDate(date.getDate() + count);
 4         var year = date.getFullYear();
 5         var month = ("0" + (date.getMonth()+1)).slice(-2);
 6         var day = ("0" + date.getDate()).slice(-2);
 7         var hours = ("0" + date.getHours()).slice(-2);
 8         var minute = ("0" + date.getMinutes()).slice(-2);
 9         var second = ("0" + date.getSeconds()).slice(-2);
10 
11         var endDate = year + "-"+ month +"-"+ day +" "+ hours +":"+ minute +":" + second;
12 
13         return endDate;
14     }
15 
16     console.log(calculateDate('2018-5-26 23:50:32',30)); // 2018-06-25 23:50:32

 1 function addMonth(date,monthNum){
 2    var str = date.split('-');
 3    var day = parseInt(str[2]);
 4    var nextMonth = new Date( str[0], parseInt(str[1])+monthNum, 0);
 5    var max = nextMonth.getDate();
 6    endDate = new Date( str[0],str[1]-1+monthNum,day>max? max: day );
 7    return endDate.toLocaleDateString().match(/\d+/g).join('-');
 8 }
 9 
10 console.log(addMonth("2018-12-12",12));

 1 function addMonth(date,monthNum){
 2 
 3    var str = date.split('-');
 4    var oldDate = new Date(str[0], parseInt(str[1]), 0);
 5    var oldDay = oldDate.getDate();
 6    console.log(oldDay);
 7    var day = parseInt(str[2]);
 8    var nextMonth = new Date( str[0], parseInt(str[1])+monthNum, 0);
 9    var max = nextMonth.getDate();
10    if(day >28 && day < 31){
11            max = max - (oldDay - day);
12            console.log(max);
13    }
14    endDate = new Date( str[0],str[1]-1+monthNum,day>max? max: day );
15    return endDate.toLocaleDateString().match(/\d+/g).join('-');
16 }
17 
18 console.log(addMonth("2018-1-27",1));