null or not an object error in IE works perfectly in Firefox

[Phoebe Song]

I have a method which works fine in FF, however in IE, I get a null or not an object error. Here is the code, IE complain about parameter lp which I pass value from another method.

  function doLoadDictionary(word,lp,U){
   var X = !window.XMLHttpRequest ? new ActiveXObject('Microsoft.XMLHTTP') : new XMLHttpRequest();
   X.open('GET', U, true );
   X.onreadystatechange=function(){
      if (X.readyState == 4){
        if (X.status == 200) {
          if(U!=null){
             xmlDoc=X.responseXML;
             var eng = xmlDoc.getElementsByTagName("english");
             for(var i=0;i<eng.length;i++){
                 if(word== eng[i].childNodes[0].nodeValue.toUpperCase()){
                 slang = word;
                 var lang = xmlDoc.getElementsByTagName(lp.toLowerCase());
                 tlang = lang[i].childNodes[0].nodeValue;
                 break;
                }
             }
            slang == undefined?(document.dictionary.english.value =''):(document.dictionary.english.value =slang);
            tlang == undefined?(document.dictionary.target.value =''):(document.dictionary.target.value =tlang);
            } 
        }
      }
   }
   X.send('');
}
  

>

[Bear Bibeault]

Which line?

[Phoebe Song]

line 13, lp.toLowerCase(), IE complains lp is null or not an object.

[Bear Bibeault]

So what is lp when the error occurs?

[Phoebe Song]

doLoadDictionary function is called by another function, lp is parameter passed from the calling function. Here is the calling function.

  function showDictionary(){
  var list = document.getElementById("dOption");
  var itemName= list.options[list.selectedIndex].value;
  var langPair = itemName.split("_");
  var sl = "English";
  var tl = langPair[1];
  switch (tl){
    case "ar-AR": 
      tl = "Arabic";
      break;
    case "de-DE": 
      tl = "German";
      break;
    case "es-ES": 
     tl = "Spanish";
     break;
    case "fr-FR": 
     tl = "French";
     break;
    case "it-IT": 
     tl = "Italian";
     break;
    case "ja-JP": 
     tl = "Japanese";
     break;
    case "pt-PT": 
     tl = "Portuguese";
     break;
    case "ko-KR": 
     tl = "Korean";
     break;
    case "ru-RU": 
     tl ="Russian";
     break;
    case"zh-CN": 
     tl = "Simplified_Chinese";
     break;
    case "zh-TW": 
     tl = "Traditional_Chinese"; 
     break; }
    document.getElementById("sl").innerHTML = sl;
    document.getElementById("tl").innerHTML = tl;
    doLoadDictionary(this.words,tl,'city.xml');
}
  

last line calls function doLoadDictionary, lp is a string, value is language name.

[Phoebe Song]

Any one know what's the problem?

[Bear Bibeault]

You didn't answer my question. What is the value of lp when it fails?