addCommas function to add commas in any amount string

addCommas.js

var addCommas = function(nStr) {
                nStr += '';
                x = nStr.split('.');
                x1 = x[0];
                x2 = x.length > 1 ? '.' + x[1] : '';
                var rgx = /(\d+)(\d{3})/;
                while (rgx.test(x1)) {
                    x1 = x1.replace(rgx, '$1' + ',' + '$2');
                }
                return x1 + x2;
            };