My javascript display is disapearing! using firstchild.data for xml

[retrofill]

Hey i've got a problem with printing out an XML document:

XML doc:
http://www.deniseburrows.pwp.blueyonder.co.uk/javascript/data.xml


If i remove the comments from the lines that add the 'publisher' and 'year' nodes, nothing is displayed on the page! :/

the code is as follows:

    function doDisplay(xmlDoc)
    { var books = xmlDoc.getElementsByTagName('book');
      var txt = '';
      for (var aBook = 0;  aBook < books.length; aBook ++)
      { var book = books[aBook];
        txt += '<p>';
        txt += book.getElementsByTagName('title')[0].firstChild.data;
        txt += ', ';
        txt += book.getElementsByTagName('author')[0].firstChild.data;
        txt += ', ';
    //txt += book.getElementsByTagName('publisher')[0].firstChild.data;
        txt += ', ';
        //txt += book.getElementsByTagName('year')[0].firstChild.data;
        txt += ', ';
        txt += book.getElementsByTagName('condition')[0].firstChild.data;
        txt += ', ';
        txt += book.getElementsByTagName('price')[0].firstChild.data;
 
        txt += '</p>\n';
      }
      displayDiv.innerHTML = txt;// + anothertxt;
    }

[Logician]

Hey i've got a problem with printing out an XML document:

XML doc:
http://www.deniseburrows.pwp.blueyonder.co.uk/javascript/data.xml

Not all of your records contain publisher or year tags, and you are not testing for their presence. This must be causing errors indicated in the console. Try this function:

function getElemText(elem, tag)
{
 var arr, retVal="";
 
 if( (arr=elem.getElementsByTagName(tag) ) && arr[0] && arr[0].firstChild!='undefined' )
  retVal=arr[0].firstChild.data;
 
 return retVal;
}
 
/* Call like this */
 
txt += getElemText(book, 'publisher');
 
 

[retrofill]

I tried this, didn't seem to work. From what i can tell it is not getting the 'cd' records; they are not tested in that function, only the 'book' records are -

and they all have the publisher and year elements.

not sure if i'm right there, but i've tried doing those checks and it still didn't work for some reason.

[Logician]

I tried this, didn't seem to work. From what i can tell it is not getting the 'cd' records; they are not tested in that function, only the 'book' records are -

and they all have the publisher and year elements.

not sure if i'm right there, but i've tried doing those checks and it still didn't work for some reason.

That was just a usage example . I meant for you to use that function multiple times, to replace all the assignments that you have currently.

[retrofill]

I changed the pseudo code you wrote and put a check for every element, but it didn't work. Not sure what to do now.

[Logician]

I changed the pseudo code you wrote and put a check for every element, but it didn't work. Not sure what to do now.

Can you show your code as it stands, and are you getting any console errors?

[retrofill]

    <script type="text/javascript" src="xhrlib.js"></script>
    <script type="text/javascript">
 
    var displayDiv;
    var books;
    var CDs;
 
    function init(displayDivID)
    { displayDiv = document.getElementById(displayDivID);
        requestXML('data.xml', setup,true);
    //doBookDisplay();
    }
 
    function setup(xmlDoc)
    { 
    books = xmlDoc.getElementsByTagName('book');
    CDs =   xmlDoc.getElementsByTagName('cd');
    }
 
 
    function doBookDisplay()
    {
      var txt = '';
      displayDiv.innerHTML = '';
      for (var aBook = 0;  aBook < books.length; aBook ++)
      { var book = books[aBook];
 
        txt += '<p>';
 
    if(book.getElementsByTagName('title')){
            txt += book.getElementsByTagName('title')[0].firstChild.data;
    }
 
        txt += ', ';
 
    if(book.getElementsByTagName('author')){
            txt += book.getElementsByTagName('author')[0].firstChild.data;
            txt += ', ';
    }
    if(book.getElementsByTagName('publisher')){
        //txt += book.getElementsByTagName('publisher')[0].firstChild.data;
        //txt += "working--------------";
        txt += ', ';
        //this does not work- no idea why
    }
 
 
    if(book.getElementsByTagName('year')){
            //txt += book.getElementsByTagName('year')[0].firstChild.data;
            txt += ', ';
        //this does not work- no idea why
    }
 
    if(book.getElementsByTagName('condition')){
            txt += book.getElementsByTagName('condition')[0].firstChild.data;
        txt += ', ';
    }
 
 
 
    if(book.getElementsByTagName('price')){
        txt += book.getElementsByTagName('price')[0].firstChild.data;
    }
 
        txt += '</p>\n';
 
      }
      displayDiv.innerHTML = txt;// + anothertxt;
    }
 
 
 
    function doCDDisplay(xmlDoc)
    {
      var txt = '';
      displayDiv.innerHTML = 'cv';
      for (var aCD = 0;  aCD < CDs.length; aCD ++)
      { var cd = CDs[aCD];
 
        txt += 'lkjlkj<p>';
 
    if(cd.getElementsByTagName('title')){
            //txt += cd.getElementsByTagName('title')[0].firstChild.data;
    }
 
        txt += ', ';
 
    if(cd.getElementsByTagName('artist')){
            //txt += cd.getElementsByTagName('artist')[0].firstChild.data;
            txt += ', ';
    } 
    if(book.getElementsByTagName('condition')){
            //txt += book.getElementsByTagName('condition')[0].firstChild.data;
        txt += ', ';
    }       
    if(cd.getElementsByTagName('year')){
            //txt += cd.getElementsByTagName('year')[0].firstChild.data;
            txt += ', ';
        //this does not work- no idea why
    }       
 
    if(cd.getElementsByTagName('price')){
        //txt += cd.getElementsByTagName('price')[0].firstChild.data;
    }
 
        txt += '</p>\n';
 
      }
      displayDiv.innerHTML = txt;// + anothertxt;
    }
    function here(){
        displayDiv.innerHTML = 'cleared';
    }
 
    </script>

http://www.deniseburrows.pwp.blueyon...uk/javascript/

Theres no error messages being displayed.
Press the 'book' button.

Its a mess as you can see, but if i take the comments off the areas actually displaying the publisher and year within the book function, nothing displays when the button is pressed.

[retrofill]

I just added this within the for loop (after the declaration of 'book')

alert( book.getElementsByTagName('publisher').length );

0 is supposed to show an error in the book declaration

and the error check returns 1 except for once, which means theres a problem. Not sure what it is though.

Anybody got any suggestions?

[Logician]

Its a mess as you can see, but if i take the comments off the areas actually displaying the publisher and year within the book function, nothing displays when the button is pressed.

You didn't use the code I gave you.
The test

 if( getElementsByTagName('xx') )

does not return false if there are no such tags.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
          "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type"
          content="text/html; charset=ISO-8859-1"/>
    <title>Example 16-1 - (Taken from Peter Coxshead's Example Material and edited for Homework)       </title>
    <script type="text/javascript" src="xhrlib.js"></script>
    <script type="text/javascript">
 
    function getElemText(elem, tag)
    {
     var arr, retVal="";
 
     if( (arr=elem.getElementsByTagName(tag) ) && arr[0] && arr[0].firstChild!='undefined' )
      retVal=arr[0].firstChild.data;
 
     return retVal;
    }
 
    var displayDiv;
    var books;
    var CDs;
 
    function init(displayDivID)
    { displayDiv = document.getElementById(displayDivID);
      requestXML('data.xml', setup,true);
 
    }
 
    function setup(xmlDoc)
    { 
   books = xmlDoc.getElementsByTagName('book');
   CDs =   xmlDoc.getElementsByTagName('cd');
    }
 
 
 function doBookDisplay()
 {
  var txt = '', t;
  displayDiv.innerHTML = '';
 
 
   for (var aBook = 0;  aBook < books.length; aBook ++)
   {
    var book = books[aBook];
 
    txt += '<p>';
 
 
    txt += getElemText(book, 'title');   
    txt += ', ';
    txt += getElemText(book, 'author');  
    txt += ', ';
 
    if( (t=getElemText(book, 'publisher'))!='')
    {
     txt += t + "working--------------"
     txt += ', ';
    }
 
    if( (t=getElemText(book, 'year'))!='')
    {
     txt += t;
     txt += ', ';
    }
 
    if( (t=getElemText(book, 'condition'))!='')
    {
     txt += t;
     txt += ', ';
    }
 
    t+=getElemText(book, 'price');
    txt += '</p>\n';
 
   }
      displayDiv.innerHTML = txt;// + anothertxt;
 }
 
 
 
 function doCDDisplay(xmlDoc)
 {
  var txt = '', t;
 
  displayDiv.innerHTML = 'cv';
 
  for (var aCD = 0;  aCD < CDs.length; aCD++)
  { 
   var cd = CDs[aCD];
 
   txt += '<p>';
 
   if((t=getElemText(cd, 'condition'))!='')
   {
    txt+=t;
    txt += ', ';
   }
 
   if((t=getElemText(cd, 'artist'))!='')
   {
    txt+=t;
    txt += ', ';
   }  
 
   if((t=getElemText(cd, 'year'))!='')
   {
    txt+=t;
    txt += ', ';
   }       
 
   if((t=getElemText(cd, 'price'))!='')
   {
    txt+=t;
    txt += ', ';
   }
 
   txt += '</p>\n';
 
  }
 
  displayDiv.innerHTML = txt;
 }
 
 function here()
 {
  displayDiv.innerHTML = 'cleared';
 }
 
     </script>
  </head>
 
  <body onload="init('display');">
    <h1>Books and Books</h1>
    <p>The data below was obtained from <a href="data.xml">data.xml</a> on the same web server as  this page.</p>
 
    <input type="button" value="Books" onclick="doBookDisplay()" />
    <input type="button" value="CDs"   onclick="doCDDisplay()" />
 
    <div id="display" onload="doBookDisplay();"></div>
 
    <input type="button" value="Next" onclick="step('i01')" />
  </body>
</html>
 
 

I'll let you decide the re-write fee.

[retrofill]

:p thanks that works great