js根据年月获取周

js根据年月获取这个月的所有周

额这是俺第一次写博客有点小激动，写了一个小功能，有问题请指导，没有注释不要怼俺。

/**
 * @package year 年
 * @package month 月
 * @return Object key值是当前第几周   value值是当前一周的7天的日期
 */
function getWeek(year, month) {
    year = year || (new Date()).getFullYear();
    month = month || (new Date()).getMonth();

    let fnToDub = time => time < 10 ? ('0' + time) : +time,
        fnGenerateDate = (time, end) => {
            let j = +time, array = [], i = 0;
            for (; j <= +end; j++) {
                array.push(j)
            }
            if (array.length < 7) {
                for (; array.length < 7; i++) {
                    array.push(i + 1);
                }
            }
            return array;
        };
    const d = new Date();
    d.setFullYear(year, month - 1, 1);
    let w1 = d.getDay() === 0 ? 7 : d.getDay();
    d.setFullYear(year, month, 0);
    const dd = d.getDate();
    const d1 = w1 !== 1 ? 7 - w1 + 2 : 1;
    const week_count = Math.ceil((dd - d1 + 1) / 7);
    let allWeek = {}, i = 0;
    for (; i < week_count; i++) {
        const sunday = fnToDub((d1 + i * 7) + 6);
        const start = year + '' + fnToDub(month) + '' + fnToDub(d1 + i * 7);
        const end = sunday <= dd ? year + '' + fnToDub(month) + '' + sunday : d.getFullYear() + '' + (d.getMonth() + 1) + '' + fnToDub(d.getDate());
        if (sunday > dd) d.setFullYear(year, fnToDub(month) - 1, sunday);
        allWeek[(i + 1)] = {
            start: start,
            end: end
        }
    }


    function g() {
        const num1 = new Date(year, month - 1, 0).getDate(),
            day = +allWeek[1].start.slice(-2) - 1;
        let ary = [], i = 1, j = 0;
        for (; i <= (7 - day); i++) {
            ary.unshift(num1 - i + 1);
        }
        for (; j < day; j++) {
            ary.push(j + 1)
        }
        return day > 0 ? ary : false;
    }

    if (g()) allWeek[0] = g();
    let obj = {}, dayType1 = +allWeek[1].start.slice(-2) === 1;
    for (let k in allWeek) {
        obj[dayType1 ? k : +k + 1] = allWeek[k].length ? allWeek[k] : fnGenerateDate(allWeek[k].start.slice(-2), allWeek[k].end.slice(-2));
    }
    return obj
}


console.log(getWeek(2019, 12));