[javascript] errors in IE 7/8

[ELD]

I currently us the below code for javascript insertion which works fine in FF & Opera but gives errors in IE.

(this was from a tutorial i found)

// add simple text
function addText(Text)
{
var obj = document.form.message;
obj.focus();

if (document.selection && document.selection.createRange) // Internet Explorer
{
sel = document.selection.createRange();
if (sel.parentElement() == obj)
{
sel.text = Text;
}
}

else if (obj != "undefined") // Firefox
{
var longueur = parseInt(obj.textLength);
var selStart = obj.selectionStart;
var selEnd = obj.selectionEnd;

obj.value = obj.value.substring(0,selStart) + Text + obj.value.substring(selEnd,longueur);
}

else
{
obj.value += Text;
}

obj.focus();
}

// wrap code in tags or just simply add them by themselves
function addTags(Tag, fTag)
{
var obj = document.form.message;
obj.focus();

// Internet Explorer
if (document.selection && document.selection.createRange)
{
sel = document.selection.createRange();
if (sel.parentElement() == obj)
{
sel.text = Tag + sel.text + fTag;
}
}

// Firefox
else if (obj != "undefined")
{
var longueur = parseInt(obj.textLength);
var selStart = obj.selectionStart;
var selEnd = obj.selectionEnd;

obj.value = obj.value.substring(0,selStart) + Tag + obj.value.substring(selStart,selEnd) + fTag + obj.value.substring(selEnd,longueur);
}

else
{
obj.value += Tag + fTag;
}

obj.focus();
}


Here is a screenshot of the error:
http://i43.photobucket.com/albums/e397/clericvash/jserror.jpg

I am no good at all with JS so i don't know what it means?

[Reiger]

For a start consider your type checking:

if(obj != 'undefined')


Is wrong for two reasons. First of all you are comparing an object (possibly null) with a string. You do this to check whether or not a variable has been set, but what if it is null. Second problem is already alluded to: this is the wrong way to check if a variable has been set. Use: typeof(obj) = typeString. Like this:

if(typeof(obj) != 'undefined')

[ELD]

Wow that actually fixed the errors in IE 8. Thanks a lot!