Function that adds commas to numbers 1,000 or greater

Add commas.js

function numberFormat(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;
}