js 时间加减

//js格式化时间 "yyyy-MM-dd hh:mm:ss"
Date.prototype.Format = function (fmt) {
    var o = {
        "M+": this.getMonth() + 1, //月份
        "d+": this.getDate(), //日
        "h+": this.getHours(), //小时
        "m+": this.getMinutes(), //分
        "s+": this.getSeconds(), //秒
        "q+": Math.floor((this.getMonth() + 3) / 3), //季度
        "S": this.getMilliseconds() //毫秒
    };
    if (/(y+)/.test(fmt))
        fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
    for (var k in o)
        if (new RegExp("(" + k + ")").test(fmt))
            fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
    return fmt;
}
Date.prototype.addDays = function (d) {
    this.setDate(this.getDate() + d);
};
Date.prototype.addWeeks = function (w) {
    this.addDays(w * 7);
};
Date.prototype.addMonths = function (m) {
    var d = this.getDate();
    this.setMonth(this.getMonth() + m);
    if (this.getDate() < d)
        this.setDate(0);
};
Date.prototype.addYears = function (y) {
    var m = this.getMonth();
    this.setFullYear(this.getFullYear() + y);
    if (m < this.getMonth()) {
        this.setDate(0);
    }
};

var now = new Date();
now.addDays(1);//加减日期操作
alert(now.Format("yyyy-MM-dd"));