JavaScript--前端开发工作中常见的时间处理问题

 1 　　Date.prototype.formatDate=function(format){
 2             var o = {
 3                 "M+": this.getMonth()+1 , //月份 
 4                 "d+": this.getDate(), //日 
 5                 "h+": this.getHours(), //小时 
 6                 "m+": this.getMinutes(), //分 
 7                 "s+": this.getSeconds(), //秒 
 8                 "q+": Math.floor((this.getMonth() + 3) / 3), // 季度
 9                 "S": this.getMilliseconds() // 毫秒
10             };
11             // 根据y的长度来截取年
12             if (/(y+)/.test(format)){ 
13                 //console.log(RegExp.$1);yyyy
14                 format = format.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
15             }
16 
17             // console.log(format);1999-MM-DD 
18             for (var k in o){
19                 if (new RegExp("(" + k + ")").test(format)) 
20                 format = format.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
21             }
22             return format;
23             }
24             // 用法： 
25             var time1 = new Date(99,3,2).formatDate("yyyy-MM-dd");
26             var time2 = new Date().formatDate("yyyy-MM-dd hh:mm:ss");
27             console.log(time1);//1999-04-02
28             console.log(time2);//2020-11-15 21:21:55

 function getFirstDayOfYear () {
        var date = new Date();
        date.setDate(1);
        date.setMonth(0);
        return date.formatDate('yyyy-MM-dd');;
    }
    console.log(getFirstDayOfYear())//2020-1-1

function getCurrentMonthFirstDay(currentMonth) {
        var endDate=new Date(currentMonth)
        var month=endDate.getMonth();
        var currentMonthFirstDay=new Date(endDate.getFullYear(),month,1)
        var firstDate=currentMonthFirstDay.toLocaleDateString().replace(new RegExp("/","g"),"-")
        return firstDate
        }
    console.log(getCurrentMonthFirstDay('2020-11'))//2020-11-1

　　function getCurrentMonthLastDay(currentMonth) {
        var endDate=new Date(currentMonth)
        var month=endDate.getMonth();
        var nextMonth=++month;
        var nextMonthFirstDay=new Date(endDate.getFullYear(),nextMonth,1);
        var oneDay=1000*60*60*24;
        var dateString=new Date(nextMonthFirstDay-oneDay)
        return dateString.toLocaleDateString().replace(new RegExp("/","g"),"-")
        }

　　function getFirstDayOfSeason () {
            var date = new Date();
            var month = date.getMonth();
            if(month <3 ){
                date.setMonth(0);
            }else if(2 < month && month < 6){
                date.setMonth(3);
            }else if(5 < month && month < 9){
                date.setMonth(6);
            }else if(8 < month && month < 11){
                date.setMonth(9);
            }
            date.setDate(1);
            return date.formatDate('yyyy-MM-dd');;
        }
        console.log(getFirstDayOfSeason())//2020-10-01

　　function getDiff(startDate, endDate) {
            var stime = Date.parse(new Date(startDate));
            var etime = Date.parse(new Date(endDate));
            // 两个时间戳相差的毫秒数
            var usedTime = etime - stime;
            // 计算相差的天数  
            var days = Math.floor(usedTime / (24 * 3600 * 1000));
            // 计算天数后剩余的毫秒数
            var leave1 = usedTime % (24 * 3600 * 1000);  
            // 计算出小时数  
            var hours = Math.floor(leave1 / (3600 * 1000));
            // 计算小时数后剩余的毫秒数
            var leave2 = leave1 % (3600 * 1000);        
            // 计算相差分钟数
            var minutes = Math.floor(leave2 / (60 * 1000));
            var time = days + "天" + hours + "时" + minutes + "分";
            return time;
        }
        console.log(getDiff("2020-10-01","2020-11-20"))//50天0时0分

　　function getWeekRange(date) {
            if(!date) return
            var now = new Date(date);
            var nowDayOfWeek = now.getDay();  // 星期日—>六（0->6）
            var nowDay = now.getDate();
            var nowMonth = now.getMonth();
            var nowYear = now.getYear(); // 2019年是119
            nowYear += (nowYear < 2000) ? 1900 : 0;
            var weekStartDate = new Date(nowYear, nowMonth, nowDay - nowDayOfWeek+1);  // 这周的周五
            var weekEndDate = new Date(nowYear, nowMonth, nowDay + (7 - nowDayOfWeek));   // 7- 这周的周日  &&  用5- 得到这的周五
            return weekStartDate.formatDate('yyyy-MM-dd') + " 至 " + weekEndDate.formatDate('yyyy-MM-dd');
            }
        console.log(getWeekRange("2020-11-11"))//2020-11-09 至 2020-11-15

 　　function restDayOfYear() {
            var fullyear = new Date().getFullYear();
            var nextyear = fullyear + 1;
            var lastday = new Date(new Date(nextyear,0,1) - 1); //本年的最后一毫秒：
            var now = new Date();
            var diff = lastday - now;  //毫秒数
            return Math.ceil(diff / (1000 * 60 * 60 * 24));
        }
        console.log(restDayOfYear("2020-11-15"))//47

　　function getWeekZh(value) {
        var dateArray = value.split("-");
        var zhWeek = "星期" + "日一二三四五六".charAt(new Date(dateArray[0], parseInt(dateArray[1] - 1), dateArray[2]).getDay());
        return zhWeek
        }
        console.log(getWeekZh("2020-10-10"))//星期六

 　　function compareDate(firstDate,secondDate){
            var arrayD1 = firstDate.split("-");
            var date1 = new Date(arrayD1[0],arrayD1[1],arrayD1[2]);
            var arrayD2 = secondDate.split("-");
            var date2 = new Date(arrayD2[0],arrayD2[1],arrayD2[2]);
            //日期对象可以直接进行比较
            if(date1 < date2) return true;             
                return false;
            }
        console.log(compareDate("2020-10-10","2020-11-15"))//true

 　　function getAfterDate(time,count) {   
            time.setDate(time.getDate() + count);//获取N天后的日期  
            var date = new Date(+time + 8 * 3600 * 1000);
                return date.toJSON().substr(0, 19).replace('T', ' ').replace(/-/g, '.');
        }  
        console.log(getAfterDate(new Date(),100))// 2021.02.23 22:00:36