XML DOM - Replace Node


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In this chapter, we will study about the replace node operation in an XML DOM object. As we know everything in the DOM is maintained in a hierarchical informational unit known as node and the replacing node provides another way to update these specified nodes or a text node.

Following are the two methods to replace the nodes.

  • replaceChild()
  • replaceData()

replaceChild()

The method replaceChild() replaces the specified node with the new node.

Syntax

The insertData() has the following syntax −

Node replaceChild(Node newChild, Node oldChild) throws DOMException

Where,

  • newChild − is the new node to put in the child list.

  • oldChild − is the node being replaced in the list.

  • This method returns the node replaced.

Example

The following example (replacenode_example.htm) parses an XML document (node.xml) into an XML DOM object and replaces the specified node <FirstName> with the new node <Name>.

<!DOCTYPE html>
<html>
   <head>
      <script>
         function loadXMLDoc(filename) {
            if (window.XMLHttpRequest) {
               xhttp = new XMLHttpRequest();
            } else // code for IE5 and IE6 {
               xhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            xhttp.open("GET",filename,false);
            xhttp.send();
            return xhttp.responseXML;
         }
      </script>
   </head>
   <body>
      <script>
         xmlDoc = loadXMLDoc("/dom/node.xml");

         x = xmlDoc.documentElement;

         z = xmlDoc.getElementsByTagName("FirstName");
         document.write("<b>Content of FirstName element before replace operation</b><br>");
         for (i=0;i<z.length;i++) {
            document.write(z[i].childNodes[0].nodeValue);
            document.write("<br>");
         }
         //create a Employee element, FirstName element and a text node
         newNode = xmlDoc.createElement("Employee");
         newTitle = xmlDoc.createElement("Name");
         newText = xmlDoc.createTextNode("MS Dhoni");

         //add the text node to the title node,
         newTitle.appendChild(newText);
         //add the title node to the book node
         newNode.appendChild(newTitle);

         y = xmlDoc.getElementsByTagName("Employee")[0]
         //replace the first book node with the new node
         x.replaceChild(newNode,y);

         z = xmlDoc.getElementsByTagName("FirstName");
         document.write("<b>Content of FirstName element after replace operation</b><br>");
         for (i = 0;i<z.length;i++) {
            document.write(z[i].childNodes[0].nodeValue);
            document.write("<br>");
         }
      </script>
   </body>
</html>

Execution

Save this file as replacenode_example.htm on the server path (this file and node.xml should be on the same path in your server). We will get the output as shown below −

Content of FirstName element before replace operation
Tanmay
Taniya
Tanisha

Content of FirstName element after replace operation
Taniya
Tanisha

replaceData()

The method replaceData() replaces the characters starting at the specified 16-bit unit offset with the specified string.

Syntax

The replaceData() has the following syntax −

void replaceData(int offset, int count, java.lang.String arg) throws DOMException

Where

  • offset − is the offset from which to start replacing.

  • count − is the number of 16-bit units to replace. If the sum of offset and count exceeds length, then all the 16-bit units to the end of the data are replaced.

  • arg − the DOMString with which the range must be replaced.

Example

The following example (replacedata_example.htm) parses an XML document (node.xml) into an XML DOM object and replaces it.

<!DOCTYPE html>
<html>
   <head>
      <script>
         function loadXMLDoc(filename) {
            if (window.XMLHttpRequest) {
               xhttp = new XMLHttpRequest();
            } else // code for IE5 and IE6 {
               xhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            xhttp.open("GET",filename,false);
            xhttp.send();
            return xhttp.responseXML;
         }
      </script>
   </head>
   <body>
      <script>
         xmlDoc = loadXMLDoc("/dom/node.xml");

         x = xmlDoc.getElementsByTagName("ContactNo")[0].childNodes[0];
         document.write("<b>ContactNo before replace operation:</b> "+x.nodeValue);
         x.replaceData(1,5,"9999999");
         document.write("<br>");
         document.write("<b>ContactNo after replace operation:</b> "+x.nodeValue);

      </script>
   </body>
</html>

In the above example −

  • x.replaceData(2,3,"999"); − Here x holds the text of the specified element <ContactNo> whose text is replaced by the new text "9999999", starting from the position 1 till the length of 5.

Execution

Save this file as replacedata_example.htm on the server path (this file and node.xml should be on the same path in your server). We will get the output as shown below −

ContactNo before replace operation: 1234567890

ContactNo after replace operation: 199999997890 


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