獲取任意天數的前7天

function get7DaysBefore(date) {
	var date = date || new Date(),
		timestamp, newDate;
	if (!(date instanceof Date)) {
		date = new Date(date.replace(/-/g, '-'));
	}
	timestamp = date.getTime();
	newDate = new Date(timestamp - 7 * 24 * 3600 * 1000);
	return [newDate.getFullYear(), ("0" + (newDate.getMonth() + 1)).slice(-2), newDate.getDate()].join('-');
}
var beforeSevenDay = get7DaysBefore(time);