js根据日期计算

startDom, yearDom, monthDom, dayDom, 均为计算日期的ID
endDom 为最终计算结果展示的ID

 1 //根据合同期始计算合同期止   传入CalculationDate的参数均为ID
 2 function CalculationDate(startDom, yearDom, monthDom, dayDom, endDom) {
 3     var start_date = $(startDom).val().trim();
 4     if (start_date) {
 5         var year = parseInt(start_date.substring(0, 4)),
 6             month = parseInt(start_date.substring(5, 7)),
 7             day = parseInt(start_date.substring(8));
 8         year = parseInt(year) + parseInt($(yearDom).val().trim());
 9         month = parseInt(month) + parseInt($(monthDom).val().trim());
10         if ($(dayDom).val() == "") {
11             day = parseInt(day);
12         }
13         else {
14             day = parseInt(day) + parseInt($(dayDom).val().trim());
15         }
16         if (month > 12) {
17             month = month - 12;
18             year = year + 1;
19         }
20         if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10) {
21             if (day > 31) {
22                 day = day - 31;
23                 month = month + 1;
24             }
25         } else if (month == 4 || month == 6 || month == 9 || month == 11) {
26             if (day > 30) {
27                 day = day - 30;
28                 month = month + 1;
29             }
30         } else if (month == 2) {
31             if (isLeapYear(year)) {
32                 if (day > 29) {
33                     day = day - 29;
34                     month = month + 1;
35                 }
36             } else {
37                 if (day > 28) {
38                     day = day - 28;
39                     month = month + 1;
40                 }
41             }
42         }
43 
44         if (day == 1) {
45             var newmonth = month - 1;
46             if (newmonth == 0) {
47                 month = 12;
48                 year--;
49                 day = 31;
50             } else if (newmonth == 1 || newmonth == 3 || newmonth == 5 || newmonth == 7 || newmonth == 8 || newmonth == 10) {
51                 month--;
52                 day = 31;
53             } else if (newmonth == 4 || newmonth == 6 || newmonth == 9 || newmonth == 11) {
54                 month--;
55                 day = 30;
56             } else if (newmonth == 2) {
57                 month--;
58                 if (isLeapYear(year)) {
59                     day = 29;
60                 } else {
61                     day = 28;
62                 }
63             }
64         } else {
65             day--;
66         }
67         $(endDom).val(year + "/" + month + "/" + day);
68     }
69 }
70 //判断是否为闰年
71 function isLeapYear(year) {
72     return (year % 4 == 0) && (year % 100 != 0 || year % 400 == 0);
73 }