请指点一下一个js问题

var $id = function (id) {

		return "string" == typeof id ? document.getElementById(id) : id;

	};

	var Class = {

		create: function() {

			return function() {

				this.initialize.apply(this, arguments);

			}

		}

	}

	Object.extend = function(destination, source) {

		for (var property in source) {

			destination[property] = source[property];

		}

		return destination;

	}

	var Calendar = Class.create();

	Calendar.prototype = {

		initialize: function(container, options) {

			this.Container = $id(container);//table结构容器

			this.Days = [];//日期列表

			this.SetOptions(options);

			this.Year = this.options.Year;

			this.Month = this.options.Month;

			this.SelectDay = this.options.SelectDay ? new Date(this.options.SelectDay) : null;

			this.onSelectDay = this.options.onSelectDay;

			this.onToday = this.options.onToday;

			this.onFinish = this.options.onFinish;

			this.Draw();

		},

		SetOptions: function(options) {

			this.options = {//默认值

				Year: new Date().getFullYear(),

				Month: new Date().getMonth() + 1,

				SelectDay: null,//选择日期

				onSelectDay: function(){},

				onToday: function(){},

				onFinish: function(){}

			};

			Object.extend(this.options, options || {});

		},

		//上月

		PreMonth: function() {

			//取得上月日期对象

			var d = new Date(this.Year, this.Month - 2, 1);

			//设置属性

			this.Year = d.getFullYear();

			this.Month = d.getMonth() + 1;

			//重绘日历

			this.Draw();

		},

		//下月

			

		NextMonth: function() {

			var d = new Date(this.Year, this.Month, 1);

			this.Year = d.getFullYear();

			this.Month = d.getMonth() + 1;

			this.Draw();

		},

		//上年

		PreYear: function() {

			//取得上月日期对象

			var d = new Date(this.Year, this.Month - 2, 1);

			//设置属性

			this.Year = d.getFullYear()-1;

			//重绘日历

			this.Draw();

		},

		//下年

		NextYear: function() {

			var d = new Date(this.Year, this.Month, 1);

			this.Year = d.getFullYear()+1;

			this.Draw();

		},

		Draw: function() {

			//保存日期列表

			var arr = [];

			//用当月第一天在一周中的日期值作为当月离第一天的天数

			for(var i = 1, firstDay = new Date(this.Year, this.Month - 1, 1).getDay(); i <= firstDay; i++){ arr.push(" "); }

			//用当月最后一天在一个月中的日期值作为当月的天数

			for(var i = 1, monthDay = new Date(this.Year, this.Month, 0).getDate(); i <= monthDay; i++){ arr.push(i); }

			//插入日期

			var frag = document.createDocumentFragment();

			this.Days = [];

			while(arr.length > 0){

			    //每个星期插入一个tr

			    var row = document.createElement("tr");

			    //星期

			    for(var i = 1; i <= 7; i++){

					var cell = document.createElement("td");

					var a	 = document.createElement("a"); 

					var alink = cell.appendChild(a);

					alink.innerHTML = " ";

					if(arr.length > 0){

						var d = arr.shift();

						alink.innerHTML = d;

						if(d > 0){

							this.Days[d] = alink;

							

							 var on = new Date(this.Year, this.Month - 1, d); 

							//判断是否今日 

							if(this.IsSame(on, new Date())){

								a.setAttribute("href",d);

							} 

							//判断是否选择日期 

							if(this.SelectDay && this.IsSame(on, this.SelectDay)){

								//this.onSelectDay(alink);

								a.setAttribute("href",d);

							}   

						}

					}

					row.appendChild(cell);

			    }

			    frag.appendChild(row);

			}

			//此先清空然后再插入(ie的table不能用innerHTML)

			while(this.Container.hasChildNodes()){ this.Container.removeChild(this.Container.firstChild); }

			this.Container.appendChild(frag);

			this.onFinish();

		},

		//判断是否同一日

		IsSame: function(d1, d2) {

			return (d1.getFullYear() == d2.getFullYear() && d1.getMonth() == d2.getMonth() && d1.getDate() == d2.getDate());

		}

	};