===編寫(xiě)日歷一===
  
  當(dāng)calendar.html調(diào)用 MYCAL:CALENDAR,當(dāng)月的日歷將會(huì)顯示在頁(yè)面中，函數(shù)setCal()是主要程序段，它初始化一些變量并調(diào)用drawCal()
  函數(shù)。我們也使用了三個(gè)別的函數(shù)：getMonthName()、 getDays() 和 leapYear()。讓我們從最后一個(gè)函數(shù)開(kāi)始：
  getDays()函數(shù)接收哪月值和哪年值，并且建立一個(gè)有12個(gè)元素的數(shù)組，用來(lái)存放每月的天數(shù)，哪一年用來(lái)決定是不是閏年，在閏年中二月
  是29天，而不是閏年是28天。該函數(shù)返回指定月份的天數(shù)。以下是getDays()：
  function getDays(month, year) {
   // create array to hold number of days in each month
   var ar = new Array(12);
   ar[0] = 31; // January
   ar[1] = (leapYear(year)) ? 29 : 28; // February
   ar[2] = 31; // March
   ar[3] = 30; // April
   ar[4] = 31; // May
   ar[5] = 30; // June
   ar[6] = 31; // July
   ar[7] = 31; // August
   ar[8] = 30; // September
   ar[9] = 31; // October
  ar[10] = 30; // November
   ar[11] = 31; // December
  
   // return number of days in the specified month (parameter)
   return ar[month];
  }
  如果指定的年數(shù)可以被4整除，那么leapYear()函數(shù)將返回“true”，否則返回”false“：
  function leapYear(year) {
  if (year % 4 == 0) // basic rule
   return true; // is leap year
  /* else */ // else not needed when statement is "return"
   return false; // is not leap year
  }
  getMonthName()函數(shù)返回指定月份的名字：
  function getMonthName(month) {
  // create array to hold name of each month
  var ar = new Array(12);
  ar[0] = "January";
  ar[1] = "February";
  ar[2] = "March";
  ar[3] = "April";
  ar[4] = "May";
  ar[5] = "June";
  ar[6] = "July";
  ar[7] = "August";
  ar[8] = "September";
  ar[9] = "October";
  ar[10] = "November";
  ar[11] = "December";
  
  // return name of specified month (parameter)
   return ar[month];
  }
  setCal()函數(shù)是主模塊，我們?cè)谀_本的第一行調(diào)用它。該函數(shù)為當(dāng)天（now）、和每月的第
  一天（firstDayInstance）建立一個(gè)Date對(duì)象。用這些對(duì)象，setCal()函數(shù)解析出關(guān)于一個(gè)月的第
  一天、當(dāng)日，和最后一天的所有信息。
  function setCal() {
   // standard time attributes
  var now = new Date();
  var year = now.getFullYear();
  var month = now.getMonth();
  var monthName = getMonthName(month);
  var date = now.getDate();
  now = null;
  
  // create instance of first day of month, and extract the day on which it occurs
  var firstDayInstance = new Date(year, month, 1);
  var firstDay = firstDayInstance.getDay();
  firstDayInstance = null;
  
  // number of days in current month
  var days = getDays(month, year);
  
  // call function to draw calendar
  drawCal(firstDay + 1, days, date, monthName, year);
  }