


Detailed explanation of Javascript calling XML to create linked drop-down box code examples
Two methods are used to link drop-down boxes in traditional HTML pages:
1) Directly hardcode the content in the drop-down box into the javascript of html, and call the Javascript function to write it into the drop-down box in a loop. This method is not suitable for situations where the contents of the drop-down box change frequently. Because the data source and JavaScript program are written on the same page.
<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("徐汇区","01","001"); subcat[1] = new Array("嘉定区","01","002"); subcat[2] = new Array("黄浦区","01","003"); subcat[3] = new Array("南昌市","02","004"); subcat[4] = new Array("九江市","02","005"); subcat[5] = new Array("上饶市","02","006"); onecount=6; function changelocation(locationid) { document.myform.smalllocation.length = 0; var locationid=locationid; var i; document.myform.smalllocation.options[0] = new Option('====所有地区====',''); 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="">==所有地区==</option> </select> </form> <script LANGUAGE="javascript"> <!-- changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value); //--> </script> </body> </html>
2) JavaScript reads the database directly, takes the records in the database and writes them into JavaScript, and then, like the first method, calls the JavaScript function to write to the drop-down box in a loop. This method separates the data source from JavaScript, but exposing the database connection has little practical value from a security perspective.
My method is to put the data in the drop-down box in an xml file, use javascript to read the XML file, and obtain the content in the drop-down box.
The HTML file is as follows:
<!-- 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;i<xmlObj.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 ; } //重复才有效 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;i<xmlObj.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;j<xmlObj.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中调用XML数据</title> </head> <body bgcolor="#FFFFFF"> <FORM NAME="frm"> 类型<SELECT NAME="mainclass" OnChange='setsubclass(this[selectedIndex].text)'></SELECT> <option selected value="" ></option> 子类<SELECT NAME="subclass"></SELECT> </form> </body> </html> account.xml 如下: <?xml version="1.0" encoding="GB2312"?> <item> <class display_name="未选定"> <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="网上注册"> <subclass display_name="1152000001-1152001000">zhuce_user1</subclass> <subclass display_name="1151001000-1151005000">zhuce_user2</subclass> </class> <class display_name="通讯"> <subclass display_name="1156030001-1156080000">tongxun</subclass> </class> </item>
This method separates the data source from the javascript program and is suitable for frequently changing data sources. In xmlDoc.load, you can directly call URL parameters and read remote XML to achieve loose coupling. The above application passes in IE6.0. The disadvantage is that when removing the contents of the drop-down box list, you need to
repeat the deletion operation, otherwise there will be obvious bugs. I hope some readers can correct me.
The above is the detailed explanation of Javascript calling XML to create a linked drop-down box code example. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!

RSS and XML are tools for web content management. RSS is used to publish and subscribe to content, and XML is used to store and transfer data. They work with content publishing, subscriptions, and update push. Examples of usage include RSS publishing blog posts and XML storing book information.

RSS documents are XML-based structured files used to publish and subscribe to frequently updated content. Its main functions include: 1) automated content updates, 2) content aggregation, and 3) improving browsing efficiency. Through RSSfeed, users can subscribe and get the latest information from different sources in a timely manner.

The XML structure of RSS includes: 1. XML declaration and RSS version, 2. Channel (Channel), 3. Item. These parts form the basis of RSS files, allowing users to obtain and process content information by parsing XML data.

RSSfeedsuseXMLtosyndicatecontent;parsingtheminvolvesloadingXML,navigatingitsstructure,andextractingdata.Applicationsincludebuildingnewsaggregatorsandtrackingpodcastepisodes.

RSS documents work by publishing content updates through XML files, and users subscribe and receive notifications through RSS readers. 1. Content publisher creates and updates RSS documents. 2. The RSS reader regularly accesses and parses XML files. 3. Users browse and read updated content. Example of usage: Subscribe to TechCrunch's RSS feed, just copy the link to the RSS reader.

The steps to build an RSSfeed using XML are as follows: 1. Create the root element and set the version; 2. Add the channel element and its basic information; 3. Add the entry element, including the title, link and description; 4. Convert the XML structure to a string and output it. With these steps, you can create a valid RSSfeed from scratch and enhance its functionality by adding additional elements such as release date and author information.

The steps to create an RSS document are as follows: 1. Write in XML format, with the root element, including the elements. 2. Add, etc. elements to describe channel information. 3. Add elements, each representing a content entry, including,,,,,,,,,,,. 4. Optionally add and elements to enrich the content. 5. Ensure the XML format is correct, use online tools to verify, optimize performance and keep content updated.

The core role of XML in RSS is to provide a standardized and flexible data format. 1. The structure and markup language characteristics of XML make it suitable for data exchange and storage. 2. RSS uses XML to create a standardized format to facilitate content sharing. 3. The application of XML in RSS includes elements that define feed content, such as title and release date. 4. Advantages include standardization and scalability, and challenges include document verbose and strict syntax requirements. 5. Best practices include validating XML validity, keeping it simple, using CDATA, and regularly updating.


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