How to Remove last Comma?

Use Array.join

var s = "";
n.each(function() {
    s += $(this).val() + ",";
});

becomes:

var a = [];
n.each(function() {
    a.push($(this).val());
});
var s = a.join(', ');

s = s.substring(0, s.length - 1);

You can use the String.prototype.slice method with a negative endSlice argument:

n = n.slice(0, -1); // last char removed, "abc".slice(0, -1) == "ab"

Or you can use the $.map method to build your comma separated string:

var s = n.map(function(){
  return $(this).val();
}).get().join();

alert(s);