[SOLVED] Catch a known error

[mwl707]

I am using this code to extract XML data

 

add2 = address2[position].firstChild.data ;

 

The problem is when is comes back from my php script it may or maynot contain a value (dependent on what info is stored in my database). The problem is when I try to use the variable and it has no value I get an error. Can somebody please tell me how to trap the error and continue. I hope this makes sense

 

If needed here is the full script I have highlighted the error  , the code is for a search address box ,  Thanks

 

// JavaScript search address

 

function searchaddress() {

document.getElementById("addressboxsearch").style.visibility = "visible";

if(XMLHttpRequestObject) {

 

searchstring = document.form1.nam.value

 

XMLHttpRequestObject.open("GET", "search_action.php?ss="+searchstring, true);

 

XMLHttpRequestObject.onreadystatechange = function() {

if (XMLHttpRequestObject.readyState == 4 &&  XMLHttpRequestObject.status == 200) {

var xmlDocument = XMLHttpRequestObject.responseXML;

 

coursename = xmlDocument.getElementsByTagName("sitelist");

address1 = xmlDocument.getElementsByTagName("address1");

address2 = xmlDocument.getElementsByTagName("address2");

postcode = xmlDocument.getElementsByTagName("postcode");

number1 = xmlDocument.getElementsByTagName("number1");

number2 = xmlDocument.getElementsByTagName(" number2");

contactname = xmlDocument.getElementsByTagName("contactname");

coursegroup = xmlDocument.getElementsByTagName("coursegroup");

courseprice = xmlDocument.getElementsByTagName("courseprice");

 

numres = coursename.length ;

 

var msg = "";

 

for (loop=0; loop<numres; loop++)

{

rcoursename =  coursename[loop].firstChild.data ;

 

links = "<a href= \"javascript:selected('" + rcoursename + "','" + loop + "'" + ") \"  >" + rcoursename + "</a>" ;

msg = msg + links  ;

msg = msg + "<br>" ;

 

}

document.getElementById("addressboxsearch").innerHTML  =  "<b> " + numres + " Results returned </b><br>" + msg ;

 

 

}

}

XMLHttpRequestObject.send(null);

}

} // end of function                                 

 

function selected(name,position) {

 

document.getElementById("addressboxsearch").style.visibility = "hidden";

 

document.form1.nam.value = name

document.form1.add1.value = address1[position].firstChild.data ;

 

/* error here

 

add2 = address2[position].firstChild.data ;

if (add2) { document.form1.add2.value = address2[position].firstChild.data } ;

*/

 

document.form1.pcode.value = postcode[position].firstChild.data ;

document.form1.primarycontactnumber.value = number1[position].firstChild.data ;

document.form1.contactname.value = contactname[position].firstChild.data ;

 

}