js补全日期

     function fillAllDays(arr, month) {
                const hasData = {};
                arr.map((item, index) => {
                    hasData[item.date] = index;
                });
                const cdate = new Date(); //当前日期
                const cyear = cdate.getFullYear(); //当前年份
                const cmonth = cdate.getMonth() + 1; //当前月份
                const day = cdate.getDate(); //当前日

                //获取N个月之前的日期
                cdate.setMonth(cdate.getMonth() - month);
                let syear = cdate.getFullYear() //起始年份
                let smonth = cdate.getMonth() + 1; //起始月份


                let ar = [];
                let sm = smonth;
                let sy = syear;
                for (let i = 0; i <= month; i++) {

                    let j = 1;


                    if (i == 0) {
                        j = day + 1;
                    } else {
                        if (sm == 12) {
                            sm = 1
                            sy += 1
                        } else {
                            sm += 1
                        }
                    }
                    
                    let len = getMonthLen(sy, sm);
                    if (sy === cyear && sm === cmonth) { //当前月份,截止到今天
                        len = day;
                    }
                    for (j; j <= len; j++) {
                        const day = j < 10 ? '0' + j : j.toString();
                        const smString = sm < 10 ? '0' + sm : sm.toString();
                        const date = sy.toString() + '-' + smString + '-' + day;
                        const obj = hasData[date] >= 0 ? arr[hasData[date]] : {
                            date,
                        }
                        ar.push(obj);
                    }
                }
                return ar;
                function getMonthLen(year, mon) {
                    return new Date(year, mon, 0).getDate();
                }
            }