XML DOM Parser Errors

From http://www.w3schools.com (Copyright Refsnes Data)

# XML DOM Parser Errors

When Firefox encounter a parser error, it loads an XML document containing the error

## Parser Error in Firefox

When trying to open an XML document, a parser-error may occur.

Unlike Internet Explorer, if Firefox encounters an error, it loads an XML document containing the error description.

The root node name of the XML error document is "parsererror". This is used to check if there is an error.

## XML Error

In the following code we let the parser load an XML document that is not well-formed.

(You can read more about well-formed and valid XML in our XML tutorial)

    xmlDoc=document.implementation.createDocument("","",null);
    xmlDoc.async=false;
    xmlDoc.load("note_error.xml");

    if (xmlDoc.documentElement.nodeName=="parsererror")
    {
    errStr=xmlDoc.documentElement.childNodes[0].nodeValue;
    errStr=errStr.replace(/</g, "&lt;");
    document.write(errStr);
    }
    else
    {
    document.write("XML is valid");
    }

Example explained:

1. Load the xml file
2. Check if the nodeName of the root node is "parsererror"
3. Load the error string into a variable "errStr"
4. Replace "<" characters with "&lt;" before the error string can be written as HTML

Try it yourself or just look at the XML file

Note: Only Internet Explorer will actually check your XML against the DTD. Firefox will not.

## Cross Browser Error Check

Here we have created an XML load function that checks for parser errors in both Internet Explorer and Firefox:

    function loadXMLDocErr(dname)
    {
    try //Internet Explorer
      {
      xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
      xmlDoc.async=false;
      xmlDoc.load(dname);

      if (xmlDoc.parseError.errorCode != 0)
        {
        alert("Error in line " + xmlDoc.parseError.line +
        " position " + xmlDoc.parseError.linePos +
        "\nError Code: " + xmlDoc.parseError.errorCode +
        "\nError Reason: " + xmlDoc.parseError.reason +
        "Error Line: " + xmlDoc.parseError.srcText);
        return(null);
        }
      }
    catch(e)
      {
      try //Firefox
        {
        xmlDoc=document.implementation.createDocument("","",null);
        xmlDoc.async=false;
        xmlDoc.load(dname);
        if (xmlDoc.documentElement.nodeName=="parsererror")
          {
          alert(xmlDoc.documentElement.childNodes[0].nodeValue);
          return(null);
          }
        }
      catch(e) {alert(e.message)}
      }
    try
      {
      return(xmlDoc);
      }
    catch(e) {alert(e.message)}
    return(null);
    }

Example explained - Internet Explorer:

1. The first line creates an empty Microsoft XML document object
2. The second line turns off asynchronized loading, to make sure that the parser will not continue execution of the script before the document is fully loaded
3. The third line tells the parser to load an XML document called "note_error.xml"
4. If the errorCode property of the parseError object is different from "0", alert the error and exit the function
5. If the errorCode property is "0", return the XML document

Example explained - Firefox:

1. The first line creates an empty XML document object.
2. The second line turns off asynchronized loading, to make sure that the parser will not continue execution of the script before the document is fully loaded.
3. The third line tells the parser to load an XML document called "note_error.xml".
4. If the returned document is an error document, alert the error and exit the function
5. If not, return the XML document

Try it yourself or just look at the XML file

From http://www.w3schools.com (Copyright Refsnes Data)