js 获取指定日期的前n天日期

function getDateBeforeTarget(date = new Date(), n = 0) {
    date = new Date(date);
    date.setDate(date.getDate() - n);
    const y = date.getFullYear();
    const m = padZero(date.getMonth() + 1);
    const d = padZero(date.getDate());
    return `${y}-${m}-${d}`;
    function padZero(n) {
        return n < 10 ? "0" + n : num;
    }
}