作者： 何耀
Thursday, June 5 2003 2:44 PM
傳統(tǒng)的HTML頁(yè)面中連動(dòng)下拉框采用了兩種方法：
1）直接將下拉框中的內(nèi)容hardcode于html的javascript中，調(diào)用javascript函數(shù)循環(huán)寫入下拉框中。這種方法不適用于下拉框內(nèi)容經(jīng)常改變的情況。因?yàn)閿?shù)據(jù)源和javascript程序?qū)懰涝谕豁?yè)面。
html>
head>
title>List/title>
meta http-equiv="Content-Type" content="text/html; c
harset=gb2312">
script LANGUAGE="javascript">
!--
var onecount;
onecount=0;
subcat = new Array();
subcat[0] = new Array("徐匯區(qū)","01","001");
subcat[1] = new Array("嘉定區(qū)","01","002");
subcat[2] = new Array("黃浦區(qū)","01","003");
subcat[3] = new Array("南昌市","02","004");
subcat[4] = new Array("九江市","02","005");
subcat[5] = new Array("上饒市","02","006");
onecount=6;
function changelocation(locationid)
{
document.myform.smalllocation.length = 0;
var locationid=locationid;
var i;
document.myform.smalllocation.options[0] = new Option('====所有地區(qū)====','');
for (i=0;i onecount; i++)
{
if (subcat[i][1] == locationid)
{
document.myform.smalllocation.options[document.myform.smalllocation.length]
= new Option(subcat[i][0], subcat[i][2]);
}
}
}
//-->
/script>
/head>
body>
form name="myform" method="post">
select name="biglocation"
onChange="changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value)">
option value="01" selected>上海/option>
option value="02">江西/option>
/select>
select name="smalllocation">
option selected value="">==所有地區(qū)==/option>
/select>
/form>
script LANGUAGE="javascript">
!--
changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value);
//-->
/script>
/body>
/html>
2）javascript 直接讀取數(shù)據(jù)庫(kù)，取數(shù)據(jù)庫(kù)中的記錄寫入javascript中，然后和第一種方法一樣，調(diào)用javascript函數(shù)循環(huán)寫入下拉框中。此方法將數(shù)據(jù)源與javascript分開，但,公開數(shù)據(jù)庫(kù)的連接，從安全角度說(shuō)，沒(méi)有多少實(shí)用價(jià)值。
我的方法是將下拉框中的數(shù)據(jù)放在XML文件中，用javascript讀XML文件，取得下拉框中的內(nèi)容。
HTML 文件如下：
!-- myfile.html -->
html>
head>
script language="JavaScript" for="window" event="onload">
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
var i=0;
var j=0;
var subclass_name="";
loadXML();
function loadXML(){
xmlDoc.async="false";
xmlDoc.load("account.xml");
xmlObj=xmlDoc.documentElement;
nodes = xmlDoc.documentElement.childNodes;
document.frm.mainclass.options.length = 0;
document.frm.subclass.options.length = 0;
for (i=0;ixmlObj.childNodes.length;i++){
labels=xmlObj.childNodes(i).getAttribute("display_name");
values=xmlObj.childNodes(i).text;
document.frm.mainclass.add(document.createElement("OPTION"));
document.frm.mainclass.options[i].text=labels;
document.frm.mainclass.options[i].value=values;
}
}
/script>
script language="JavaScript" >
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
var i=0;
var j=0;
function deleteOption() {
}
function setsubclass(main){
var is_selected="N";
if (document.frm.subclass.options.length!=0) {
for (i=0;i=document.frm.subclass.options.length;i++)
document.frm.subclass.options[i]=null ;
}
//重復(fù)才有效
if (document.frm.subclass.options.length!=0) {
for (i=0;i=document.frm.subclass.options.length;i++){
document.frm.subclass.options[i]=null ;
document.frm.subclass.options.remove(i);
}
}
for (i=0;ixmlObj.childNodes.length;i++){
var values="";
var lables="";
if (is_selected=="Y") return;
labels=xmlObj.childNodes(i).getAttribute("display_name");
values=xmlObj.childNodes(i).text;
//alert(labels+ " | "+main);
if (labels==main){
is_selected="Y";
for (j=0;jxmlObj.childNodes(i).childNodes.length;j++){
//subclass_name="document.frm.subclass";
labels=xmlObj.childNodes(i).childNodes(j).getAttribute("display_name");
values=xmlObj.childNodes(i).childNodes(j).text;
//alert(values);
document.frm.subclass.add(document.createElement("OPTION"));
document.frm.subclass.options[j].text=labels;
document.frm.subclass.options[j].value=values;
}
}
}
}
/script>
title>在HTML中調(diào)用XML數(shù)據(jù)/title>
/head>
body bgcolor="#FFFFFF">
FORM NAME="frm">
類型SELECT NAME="mainclass" OnChange='setsubclass(this[selectedIndex].text)'>/SELECT>
option selected value="" >/option>
子類SELECT NAME="subclass">/SELECT>
/form>
/body>
/html>
account.xml 如下：
?xml version="1.0" encoding="GB2312"?>
item>
class display_name="未選定">
subclass display_name="">Not Available/subclass>
/class>
class display_name="95788主叫卡">
subclass display_name="1152069589-1152069638">dangdang1/subclass>
subclass display_name="1152081031-1152081080">dangdang2/subclass>
subclass display_name="1152547201-1105254750">dangdang3/subclass>
subclass display_name="1152548401-1152548700">dangdang4/subclass>
subclass display_name="1152548701-1152549000">dangdang5/subclass>
subclass display_name="1156000001-1156010000">dangdang6/subclass>
/class>
class display_name="網(wǎng)上注冊(cè)">
subclass display_name="1152000001-1152001000">zhuce_user1/subclass>
subclass display_name="1151001000-1151005000">zhuce_user2/subclass>
/class>
class display_name="通訊">
subclass display_name="1156030001-1156080000">tongxun/subclass>
/class>
/item>
此方法將數(shù)據(jù)源與javascript程序分開，適合經(jīng)常變化的數(shù)據(jù)源。xmlDoc.load中可以直接調(diào)用URL參數(shù),讀取遠(yuǎn)程XML，實(shí)現(xiàn)松耦合。以上應(yīng)用在IE6.0中通過(guò)。不足之處是在去除下拉框列表內(nèi)容時(shí)需要
重復(fù)執(zhí)行刪除操作，否則會(huì)有明顯的bug.希望有讀者能給指正。
