Remove Duplicate words in javascript

<SCRIPT LANGUAGE="Javascript">
<!--
function remove_list()
{
var count = 0;
var list = document.form1.list.value;
list =list.replace(/\r/gi, "\n");
list = list.replace(/\n+/gi, "\n");

var listvalues = new Array();
var newlist = new Array();

listvalues = list.split("\n");

var hash = new Object();

for (var i=0; i<listvalues.length; i++)
{
if (hash[listvalues[i].toLowerCase()] != 1)
{
newlist = newlist.concat(listvalues[i]);
hash[listvalues[i].toLowerCase()] = 1
}
else { count++; }
}
document.form1.list.value = newlist.join("\r\n");

}
//-->
</SCRIPT>

</HEAD>

<!-- STEP TWO: Copy this code into the BODY of your HTML document -->

<BODY>

<CENTER>
<FORM ACTION="" NAME="form1" ID="form1">
<TABLE BORDER=1 CELLPADDING=5 BORDERCOLOR="#FF0000" BGCOLOR="#FFFFFF">
<TR>
<TD>Paste list to be de-duped here<BR>(one value per line)<P><TEXTAREA NAME="mainlist" COLS=30 ROWS=20></TEXTAREA></TD>
</TR>
<TR><TD align="center"><input type="button" onClick="remove_list();" value="De-Dupe List!"></TD></TR>
</TABLE>
</center>
</FORM>

For Example -:
Input-: Apple,Mango,Apple,Orange

Output -: Apple,Mango,Orange