JS format current time and date calculation

// The first one means that it is still a few days away from today , Such as 0 Today ,1 For tomorrow ,-1 Yesterday 
// The second digit indicates the specified date , Default not to today , Support formats '2020-10-10', '2020/01/01'
function getTargetDate(num = 0, baseDate = null) {
    
    let tarDate = ''// Target date 
    if (baseDate) {
    
        tarDate = new Date(baseDate);
    } else {
    
        tarDate = new Date();
    }

    // If num Not for 0  Explain the passage of time , The base time needs to be converted into the form of timestamp for calculation 
    if (num !== 0) {
    
        tarDate = tarDate.getFullYear() + '-' + (tarDate.getMonth() + 1) + '-' + tarDate.getDate() + ' 00:00:00';// Year-Month-Date 00:00:00
        tarDate = Date.parse(tarDate.replace(/-/g, '/'));// Converts the specified time to a timestamp ,ie I won't support it ‘/’,Date.parse(Year-Month-Date)
        tarDate += (86400000) * num;// Modified timestamp ,24*60*60 = 86400000  Milliseconds of the day 
        tarDate = new Date(tarDate);// Time stamp converted to time 
        // tarDate = new Date(tarDate.setDate(tarDate.getDate() + num))//todo  This line replaces the four lines above 
    }

    // hold new Date() In the form of   format 
    const weekday = [
        " Sunday ",
        " Monday ",
        " Tuesday ",
        " Wednesday ",
        " Thursday ",
        " Friday ",
        " Saturday ",
    ];
    const y = tarDate.getFullYear();
    let month = (tarDate.getMonth() + 1);
    month = month < 10 ? "0" + month : month
    let date = tarDate.getDate(); // direct date Plus or minus, there will be problems when you meet people across the moon ,getDate Get a number after ,01-2 = -1
    date = date < 10 ? "0" + date : date
    const d = weekday[tarDate.getDay()];
    let h;
    h = tarDate.getHours() < 10 ? "0" + tarDate.getHours() : tarDate.getHours()
    let m;
    m = tarDate.getMinutes() < 10 ? "0" + tarDate.getMinutes() : tarDate.getMinutes()
    let s;
    s = tarDate.getSeconds() < 10 ? "0" + tarDate.getSeconds() : tarDate.getSeconds()
    let resDate = `${
      y}-${
      month}-${
      date}`
    let resNumDate = '' + y + month + date
    let currentTime = `${
      h}:${
      m}:${
      s}`

    return {
    
        year: y,
        month: month,
        date: date,
        weekday: d,
        hour: h,
        minute: m,
        second: s,
        resDate: resDate,//Year-Month-Date
        resNumDate: resNumDate,//YearMonthDte
        currentTime: currentTime,//xx:xx:xx
    }
}

// Supported input parameters 
getTargetDate().currentTime // 16:05:05
getTargetDate().resNumDate //20201212  same day 
getTargetDate().resDate//2020-12-12  same day 
getTargetDate(-1).resDate//2020-12-11  A day earlier 
getTargetDate().weekday // Saturday 
getTargetDate(2,'2022-01-18').resDate //2022-01-20, Appoint 2022-01-18 Two days later