[Javascript] need help for my swaping function

[patcito at gmail.com (Patrick Aljord)]

i wrote a function that adds tags to a textbox and remove them if
there are in already like in delicious:
function addTag(ele) {
    var thisTag = ele.innerHTML;
    var taglist = document.getElementById('tags');
    var tags = taglist.value.split(', ');

    // if the tag is in the list, we remove it
    if (tags.contains(thisTag)) {
        tags = tags.remove(thisTag);
        ele.className = 'unselected';

    // else we add it
    } else {
        tags.splice(0, 0, thisTag);
        ele.className = 'selected';
    }

    taglist.value = tags.join(', ');

    document.getElementById('tags').focus();
}

Array.prototype.contains = function (ele) {
    for (var i = 0; i < this.length; i++) {
        if (this[i] == ele) {
            return true;
        }
    }
    return false;
};

Array.prototype.remove = function (ele) {
    var arr = new Array();
    var count = 0;
    for (var i = 0; i < this.length; i++) {
        if (this[i] != ele) {
            arr[count] = this[i];
            count++;
        }
    }
    return arr;
};
and in my code I have:
<p><label for="tags">Tags</label><br/>
<input id="tags" name="tags" size="40" type="text" /></p>

<span id="tag1" name="tag1" onclick="addTag(this)">
tag1
</span>

<span id="tag2" name="tag2" onclick="addTag(this)">
tag2
</span>

it works well, when I click on a tag it gets displayed in the textbox
and when I click on the tag again it removes it correctly. But if I
write a tag in the textbox that also feature in one of the tag span,
then if I click in the tag span it won't remove it. I will add it
again to the list as if the script didn't check tags added by hand.

Any idea what's wrong?

thanx in advance

Pat