//添加天Date.prototype.addDays = function (d) {    this.setDate(this.getDate() + d);};//添加周Date.prototype.addWeeks = function (w) {    this.addDays(w * 7);};//添加月Date.prototype.addMonths = function (m) {    var d = this.getDate();    this.setMonth(this.getMonth() + m);    if (this.getDate() < d)        this.setDate(0);};//添加年Date.prototype.addYears = function (y) {    var m = this.getMonth();    this.setFullYear(this.getFullYear() + y);    if (m < this.getMonth()) {        this.setDate(0);    }};