My substring() isn't working

What am not getting about substring()?
I'm trying to separate out dd and yy
from input coming in as mm/dd/yy.
(My mm is parsing out correctly).

var mm = mydate.substring(0, mydate.indexOf("/"));
var ddlength = (mydate.lastIndexOf("/")-1-mydate.indexOf("/") );
var ddstartat = (mydate.indexOf("/")+1);
var dd = mydate.substring(ddstartat, ddlength);
var yylength = (mydate.length - 1 - mydate.lastIndexOf("/"));
var yystartat = (mydate.lastIndexOf("/")+1);
var yy = mydate.substring(yystartat, yylength);

Change substring to substr. These are two different methods.

<script type = "text/javascript">
var mydate = "12/23/08"
var mm = mydate.substr(0, mydate.indexOf("/"));
var ddlength = (mydate.lastIndexOf("/")-1-mydate.indexOf("/") );
var ddstartat = (mydate.indexOf("/")+1);
var dd = mydate.substr(ddstartat, ddlength);
var yylength = (mydate.length - 1 - mydate.lastIndexOf("/"));
var yystartat = (mydate.lastIndexOf("/")+1);
var yy = mydate.substr(yystartat, yylength);

alert (mm + "/" + dd + "/" + yy)

</script>

The syntax is substr(x,y) where x is the start position of the substring and y is the length of the substring to be returned.



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