js获取前几天的时间及时间区间

/** * 以startDate为开始日期，计算时隔days天之后 的日期区间 * @param startDate 开始日期 * @param days 时间间隔天数 */function getDateInterval(startDate, days) { ???var start; ???var end; ???if (startDate instanceof Date) { ???????start = startDate.getFullYear() + "/" + (startDate.getMonth() + 1) + "/" + startDate.getDate(); ???????var startAfterDays = startDate.setDate(startDate.getDate() - days); ???????startAfterDays = new Date(startAfterDays); ???????end = startAfterDays.getFullYear() + "/" + (startAfterDays.getMonth() + 1) + "/" + startAfterDays.getDate(); ???} ???return end + "~" + start;}/** * 获得昨天的日期 * @returns {Date} */function getYesterdayDate() { ???var date = new Date(); ???date.setTime(date.getTime() - 24 * 60 * 60 * 1000); ???return date;}/** * 根据时间间隔天数，获取具体日期区间 * @param days 时间间隔天数 * @returns {string} */function getStartAndEndDate(days) { ???var now = new Date(); ???var start = now.getFullYear() + "/" + (now.getMonth() + 1) + "/" + now.getDate(); ???var nowAfterDays = now.setDate(now.getDate() - days); ???nowAfterDays = new Date(nowAfterDays); ???var end = nowAfterDays.getFullYear() + "/" + (nowAfterDays.getMonth() + 1) + "/" + nowAfterDays.getDate(); ???return end + "~" + start;}