JS 获取当前日期的前几天或者后几天

/**
 * 计算时间
 * @param {number} day 距当前天数，可传负数
 * @param {boolean} isTime 是否显示具体时间
 */
export const getDay = (day, isTime) => {
	var today = new Date();
	var targetday_milliseconds = today.getTime() + 1000 * 60 * 60 * 24 * day;
	today.setTime(targetday_milliseconds);
	var tYear = today.getFullYear();
	var tMonth = today.getMonth() + 1;
	var tDate = today.getDate();
	var tHours, tMinutes, tSeconds;
	if (isTime) {
		tHours = add0(today.getHours());
		tMinutes = add0(today.getMinutes());
		tSeconds = add0(today.getSeconds());
	} else {
		tHours = '00';
		tMinutes = '00';
		tSeconds = '00';
	}
	return tYear + '-' + tMonth + '-' + tDate + ' ' + tHours + ':' + tMinutes + ':' + tSeconds;
};