[자바스크립트] 현재 중심적인 시간 표시하기

export const SECOND_TO_MS = 1000;
export const MINUTE_TO_SECOND = 60;
export const HOUR_TO_SECOND = MINUTE_TO_SECOND * 60;
export const DAY_TO_SECOND = HOUR_TO_SECOND * 24;
export const WEEK_TO_DAY = 7;
export const WEEK_TO_SECOND = WEEK_TO_DAY * DAY_TO_SECOND;
// (365.24 / 12).toFixed(2)
export const MONTH_TO_DAY = 30.43;
export const MONTH_TO_SECOND = MONTH_TO_DAY * DAY_TO_SECOND;
// Consider leap year
export const YEAR_TO_DAY = 365.24;
export const YEAR_TO_SECOND = YEAR_TO_DAY * DAY_TO_SECOND;
 
export default function formatToReadableTime(dateString: string): string {
    const now = new Date().getTime();
    const date = new Date(dateString).getTime();
    if (Number.isNaN(date)) {
        return "어떤 오후";
    }
 
    const { floor } = Math;
    const diffToSeconds = (now - date) / SECOND_TO_MS;
    const diffToDay = floor(diffToSeconds / DAY_TO_SECOND);
    const lessThanDay = diffToSeconds < DAY_TO_SECOND;
 
    if (lessThanDay) {
        if (diffToSeconds < 5 * MINUTE_TO_SECOND) {
            return "방금";
        }
 
        if (diffToSeconds < HOUR_TO_SECOND) {
            return `${floor(diffToSeconds / MINUTE_TO_SECOND)}분 전`;
        }
 
        return `${floor(diffToSeconds / HOUR_TO_SECOND)}시간 전`;
    }
 
    if (diffToDay < WEEK_TO_DAY) {
        return `${diffToDay}일 전`;
    }
 
    if (diffToDay < 2 * MONTH_TO_DAY) {
        return `${floor(diffToDay / WEEK_TO_DAY)}주 전`;
    }
 
    if (diffToDay < YEAR_TO_DAY) {
        return `${floor(diffToDay / MONTH_TO_DAY)}개월 전`;
    }
 
    return `${floor(diffToDay / YEAR_TO_DAY)}년 전`;
}