js获取选中日期的当周的周一和周日

js获取选中日期的当周的周一和周日

 第一种方法（推荐）：

　　function getWeekStr(str) {
        // 将字符串转为标准时间格式
        str2 = Date.parse(str);
        let date = new Date(str2);
        let month = date.getMonth() + 1;
        let week = getWeekFromDate(date);
        if (week === 0) {//第0周归于上月的最后一周
            month = date.getMonth();
            let dateLast = new Date();
            let dayLast = new Date(dateLast.getFullYear(), dateLast.getMonth(), 0).getDate();
            let timestamp = new Date(new Date().getFullYear(), new Date().getMonth() - 1, dayLast);
            week = getWeekFromDate(new Date(timestamp));
        }
        let time = month + "月第" + week + "周";
        return time;
    }

    function getWeekFromDate(date) {
        // 将字符串转为标准时间格式
        let w = date.getDay();//周几
        if (w === 0) {
            w = 7;
        }
        let week = Math.ceil((date.getDate() + 6 - w) / 7) - 1;
        return week;
    }

    console.log("2018-02-3---" + getWeekStr("2018-02-3"));
    console.log("2018-02-4---" + getWeekStr("2018-02-4"));
    console.log("2018-02-5---" + getWeekStr("2018-02-5"));
    console.log("2018-02-12---" + getWeekStr("2018-02-12"));
    console.log("2018-02-19---" + getWeekStr("2018-02-19"));
    console.log("2018-02-28---" + getWeekStr("2018-02-28"));
    console.log("2018-03-1---" + getWeekStr("2018-03-1"));
    console.log("2018-03-5---" + getWeekStr("2018-11-1"));
    console.log("2018-08-27---" + getWeekStr("2018-12-01"));

第二种方法（比较复杂）：　　

console.log(getNowDateAndNowWeek(1539187200000));
    
    /**
     * 获取当月的第几周
     * a = d = 当前日期
     * b = 6 - w = 当前周的还有几天过完(不算今天)
     * a + b 的和在除以7 就是当天是当前月份的第几周
    */
    function getMonthWeek(a, b, c) {

        var date = new Date(a, parseInt(b) - 1, c), w = date.getDay(), d = date.getDate();
        return Math.ceil(
            (d + 6 - w) / 7
        );
    };

    
    /**
     * 获取选择当前的第几周，当前的周一、周日
     * time 选择日期的时间戳
     */
    function getNowDateAndNowWeek(time) {
        //选中的时间戳
        var timestamp = time;
        var serverDate = new Date(time);

        //本周周日的的时间
        var sundayTiem = timestamp + ((7 - serverDate.getDay()) * 24 * 60 * 60 * 1000)
        var SundayData = new Date(sundayTiem);
        //年
        var tomorrowY = SundayData.getFullYear();
        //月
        var tomorrowM = (SundayData.getMonth() + 1 < 10 ? '0' + (SundayData.getMonth() + 1) : SundayData.getMonth() + 1);
        //日
        var tomorrowD = SundayData.getDate() < 10 ? '0' + SundayData.getDate() : SundayData.getDate();
        console.log('周日：  ' + tomorrowY + '-' + tomorrowM + '-' + tomorrowD);

        // 本周周一的时间
        var mondayTime = timestamp - ((serverDate.getDay() - 1) * 24 * 60 * 60 * 1000)
        var mondayData = new Date(mondayTime);
        //年
        var mondayY = mondayData.getFullYear();
        //月
        var mondayM = (mondayData.getMonth() + 1 < 10 ? '0' + (mondayData.getMonth() + 1) : mondayData.getMonth() + 1);
        //日
        var mondayD = mondayData.getDate() < 10 ? '0' + mondayData.getDate() : mondayData.getDate();
        var nowWeek = getMonthWeek(tomorrowY, tomorrowM, tomorrowD);
        //输出值
        var config = {
            SunDay: tomorrowY + '/' + tomorrowM + '/' + tomorrowD,
            Monday: mondayY + '/' + mondayM + '/' + mondayD,
            nowWeek: nowWeek
        }
        return config;
    }