八. 綜合應(yīng)用

　　最后一個例子演示JavaScript對象的重要性。首先設(shè)置好一個 Calendar(日歷)對象，然后根據(jù)需要顯示任何一個月的月歷。執(zhí)行過程不復(fù)雜，只需要指定月和年為對象屬性，然后讓構(gòu)造器做其它事情即可：

＜script language="JavaScript"＞
/*　　Calendar object, calendar.js
　　　Usage:
　　　obj = new Calendar(mm, yyyy);
　　　created 15.Mar.2001

　　　copyright Melonfire, 2001. all rights reserved.
　　　http://www.melonfire.com/community/columns/trog/

　　　demonstration only - not meant for production enviroments!!
*/

// constructor
function Calendar(month, year)
{

// array of day names
this.days = new Array("Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday");

// array of month names
this.months = new Array("January", "February", "March", "April", "May",
"June", "July", "August", "September", "October", "November", "December");

// array of total days in each month
this.totalDays = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

// object properties - month and year
// correction for zero-based array index
this.month = month-1;
this.year = year;

// leap year correction
if (this.year % 4 == 0)
{
this.totalDays[1] = 29;
}

// temporary variable - used later
this.rowCount = 0;

// object method
this.display = display;

// automatically run method display() once object is initialized
this.display();
}

// function to display calendar
function display()
{

// create a Date object
// required to obtain basic date information
// get the first and last day of the month - boundary values for calendar
obj = new Date(this.year, this.month, 1);
this.firstDayOfMonth = obj.getDay();
obj.setDate(31);
this.lastDayOfMonth = obj.getDay();

// start table
document.write("＜table border=0 cellpadding=2 cellspacing=5＞");

// month display
document.write("＜tr＞＜td colspan=7 align=center＞＜font face=Arial
size=-1＞＜b＞" + this.months[this.month] + " " + this.year +
"＜/b＞＜/font＞＜/td＞＜/tr＞");

// day names
document.write("＜tr＞");
for (x=0; x＜7; x++)
{

document.write("＜td＞＜font face=Arial size=-2＞" +
this.days[x].substring(0,3) + "＜/font＞＜/td＞") ;
}
document.write("＜/tr＞");

// start displaying dates
// display blank spaces until the first day of the month
document.write("＜tr＞");
for (x=1; x＜=this.firstDayOfMonth; x++)
{
// this comes in handy to find the end of each 7-day block
this.rowCount++;
document.write("＜td＞＜font face=Arial size=-2＞ ＜/font＞＜/td＞");
}

// counter to track the current date
this.dayCount=1;
while (this.dayCount ＜= this.totalDays[this.month])
{
// use this to find out when the 7-day block is complete and display a new row
if (this.rowCount % 7 == 0)
{
document.write("＜/tr＞\n＜tr＞");
}

// print date
document.write("＜td align=center＞＜font face=Arial size=-1＞" + this.dayCount
+ "＜/font＞＜/td＞");
this.dayCount++;
this.rowCount++;
}
// end table
document.write("＜/tr＞＜/table＞");
}

// eof
＜/script＞

以下解釋一下上面代碼的工作過程：

　　最開始的幾行設(shè)置了包含月和日名的數(shù)組以及每個月中總的天數(shù)。用一個簡單的方程式來判斷某年是否為閏年，如果是的話就對二月的總天數(shù)進(jìn)行相應(yīng)修改。然后控制就傳給了對象方法display()，它負(fù)責(zé)將日歷寫到頁面上。

　　使用了Date對象和一些臨時(shí)變量之后，就創(chuàng)建了一個表格并用這個月的日期來填充好。document.write()方法負(fù)責(zé)設(shè)置 ＜table＞、＜tr＞ 和 ＜td＞ 標(biāo)記，然后將日期信息打印到表格單元中。

　　以下代碼說明如何使用這個對象：

＜html＞
＜head＞
＜script language="JavaScript" src="calendar.js"＞＜/script＞
＜/head＞

＜body bgcolor="white"＞
＜script＞ obj1 = new Calendar(2, 2005); ＜/script＞
＜script＞ obj2 = new Calendar(7, 2001); ＜/script＞
＜/body＞
＜/html＞

　　代碼運(yùn)行。

這就是全部了。我希望本文中的例子能讓你對 JavaScript對象的用途有一個正確的評價(jià)，也許還能為你在開發(fā)中使用它們提供幾個有用的思路。