var isIE = false;
var req;
function loadXMLDoc( url ) 
{
    if( window.XMLHttpRequest ){ req = new XMLHttpRequest(); req.onreadystatechange = processReqChange; req.open("GET", url, true); req.send(null); }
    else if( window.ActiveXObject ){ isIE = true; req = new ActiveXObject("Microsoft.XMLHTTP"); if(req) { req.onreadystatechange = processReqChange; req.open("GET", url, true); req.send(); }}
}
function processReqChange()
{
    if( req.readyState == 4 ) 
    {
        document.getElementById( 'info').innerHTML='';
        if( req.status == 200 ) 
        {
            clearTopicList();
            buildTopicList();
        }
        else alert("There was a problem retrieving the XML data:\n" + req.statusText );
    }
}
function loadPobs() 
{
      var prov = document.getElementById( 'prv_id' ).value;
      if( prov > 0 ) 
      {
          document.getElementById( 'info').innerHTML='<font color=maroon> cargando ... </font>';
          try { loadXMLDoc( '7_qryprov.php?prov=' + prov ); }
          catch( e ) { var msg = ( typeof e == "string" ) ? e : (( e.message ) ? e.message : "Unknown Error" ); alert( "Unable to get XML data:\n" + msg ); return; }
      }
      else
      {
          clearTopicList();
          var select = document.getElementById( "cod_zona" );
          appendToSelect( select, 0, document.createTextNode( 'Elija primero una provincia' ));
      }
}
function getElementTextNS( prefix, local, parentElem, index )
{
    var result = "";
    if( prefix && isIE ) result = parentElem.getElementsByTagName(prefix + ":" + local)[index];
    else result = parentElem.getElementsByTagName( local )[ index ];
    if( result ) 
    {
        // get text, accounting for possible whitespace (carriage return) text nodes 
        if(result.childNodes.length > 1) return result.childNodes[1].nodeValue;
        else return result.firstChild.nodeValue;    		
    }
    else return "n/a";
}
function clearTopicList()
{
    var select = document.getElementById("cod_zona"); while ( select.length > 0 ){ select.remove(0); }
}
function appendToSelect( select, value, content )
{
    var opt = document.createElement( "option" );
    opt.value = value;
    opt.appendChild( content );
    select.appendChild( opt );
}
function buildTopicList()
{
    var select = document.getElementById( "cod_zona" );
    var items = req.responseXML.getElementsByTagName( "r" );
    for ( var i = 0; i < items.length; i++ ){ appendToSelect( select, getElementTextNS( "", "c", items[i], 0 ), document.createTextNode( getElementTextNS( "", "n", items[i], 0 ))); }
}