Auto Generate Random Number through Javascript

function AutoGenRdmNumber()
{
    var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZ";
    var string_length = 6;
    var randomstring = '';
    for (var i = 0; i < string_length; i++)
 {
        var rnum = Math.floor(Math.random() * chars.length);
        randomstring += chars.substring(rnum, rnum + 1);
    }
    var d = new Date();
    var n = "TR-" + d.getDate().toString() + (d.getMonth() + 1).toString() + d.getHours().toString() + d.getMinutes().toString() + "-" + randomstring;
 
        Xrm.Page.getAttribute("new_trnumber").setValue(n);
   
}