XML DOM - Traversing

In this chapter, we will discuss XML DOM Traversing. We studied in the previous chapter how to load XML document and parse the thus obtained DOM object. This parsed DOM object can be traversed. Traversing is a process in which looping is done in a systematic manner by going across each and every element step by step in a node tree.

Example

The following example (traverse_example.htm) demonstrates DOM traversing. Here we traverse through each child node of <Employee> element.

<!DOCTYPE html>
<html>
   <style>
      table,th,td {
         border:1px solid black;
         border-collapse:collapse
      }
   </style>
   <body>
      <div id = "ajax_xml"></div>
      <script>
         //if browser supports XMLHttpRequest
         if (window.XMLHttpRequest) {// Create an instance of XMLHttpRequest object. 
            code for IE7+, Firefox, Chrome, Opera, Safari
            var xmlhttp = new XMLHttpRequest();
         } else {// code for IE6, IE5
            var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
         }
         // sets and sends the request for calling "node.xml"
            xmlhttp.open("GET","/dom/node.xml",false);
            xmlhttp.send();

         // sets and returns the content as XML DOM
            var xml_dom = xmlhttp.responseXML;
	
         // this variable stores the code of the html table
            var html_tab = '<table id = "id_tabel" align = "center">
            <tr>
               <th>Employee Category</th>
               <th>FirstName</th>
               <th>LastName</th>
               <th>ContactNo</th>
               <th>Email</th>
            </tr>';
            var arr_employees = xml_dom.getElementsByTagName("Employee");
         // traverses the "arr_employees" array
            for(var i = 0; i<arr_employees.length; i++) {
               var employee_cat = arr_employees[i].getAttribute('category');
   
               // gets the value of 'category' element of current "Element" tag

               // gets the value of first child-node of 'FirstName' 
               // element of current "Employee" tag
                  var employee_firstName =
                     arr_employees[i].getElementsByTagName('FirstName')[0].childNodes[0].nodeValue;

               // gets the value of first child-node of 'LastName' 
               // element of current "Employee" tag
                  var employee_lastName =
                     arr_employees[i].getElementsByTagName('LastName')[0].childNodes[0].nodeValue;

               // gets the value of first child-node of 'ContactNo' 
               // element of current "Employee" tag
                  var employee_contactno = 
                     arr_employees[i].getElementsByTagName('ContactNo')[0].childNodes[0].nodeValue;

               // gets the value of first child-node of 'Email' 
               // element of current "Employee" tag
                  var employee_email = 
                     arr_employees[i].getElementsByTagName('Email')[0].childNodes[0].nodeValue;

               // adds the values in the html table
               html_tab += '<tr>
                  <td>'+ employee_cat+ '</td>
                  <td>'+ employee_firstName+ '</td>
                  <td>'+ employee_lastName+ '</td>
                  <td>'+ employee_contactno+ '</td>
                  <td>'+ employee_email+ '</td>
               </tr>';
            }
         html_tab += '</table>'; 
         // adds the html table in a html tag, with id = "ajax_xml"
         document.getElementById('ajax_xml').innerHTML = html_tab; 
      </script>
   </body>
</html>

  • This code loads node.xml.

  • The XML content is transformed into JavaScript XML DOM object.

  • The array of elements (with tag Element) using the method getElementsByTagName() is obtained.

  • Next, we traverse through this array and display the child node values in a table.

Execution

Save this file as traverse_example.html on the server path (this file and node.xml should be on the same path in your server). You will receive the following output −

XML DOM traversing
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