js获取前n天的时间

惯例直接上代码:

//默认投保日期起,默认3天内的
    function start() {
        var today = new Date(new Date() - 2 * 24 * 60 * 60 * 1000);
        var h = today.getFullYear();
        var m = today.getMonth() + 1;
        var d = today.getDate();
        m = m < 10 ? "0" + m : m;
        d = d < 10 ? "0" + d : d;
        return h + "-" + m + "-" + d + " 00:00:00";
    }

获取就是当前时间算起,3天前凌晨0点0分0秒的日期